Most of these requests are reasonable by themselves, but please, for the sake of my sanity, do it one step at a time.
@evazion I apologize for how convoluted the BURs have been for you. Believe me, the series itself has not made it easy for us to figure out how to tag them here, and Fate/Grand Order continuously strives to make things worse for us.
Anyway, I picked through the second BUR that @Astolfo made and sorted the simpler rename requests into alphabetical chunks that can be requested individually. I'll just post the tentative list, excluding the complicated tags that need further discussion, and see if you're satisfied with managing several smaller BURs one at a time. I'm not sure of what you consider a manageable request size, and certain letters are far more populated than others. I did a count of how many tags would be in each BUR, so let me know if you want to shrink these even further.
ADDENDUM: Shoot, I just realized that posts with 200+ posts would warrant an alias rather than a rename. I was so engrossed with sorting everything into alphabetical chunks that I neglected to address that. Would this mean I'd have to filter out the aliases from all of these renames and make new BURs for those?
BUR – RENAME A – Ca (50 tags)
rename abigail_williams_(fate/grand_order) -> abigail_williams_(fate)
rename alcides_(fate/strange_fake) -> alcides_(fate)
rename alice_(fate/extra) -> alice_(fate)
rename anne_bonny_(fate/grand_order) -> anne_bonny_(fate)
rename antonio_salieri_(fate/grand_order) -> antonio_salieri_(fate)
rename archer -> archer_(fate/stay_night)
rename archer_(prisma_illya) -> archer_(fate/kaleid_liner)
rename archer_alter -> archer_(alter)_(fate/grand_order:_first_order)
rename archer_class_(fate/stay_night) -> archer_class_(fate)
rename archer_(fate/prototype) -> gilgamesh_(fate/prototype)
rename archer's_master_(fate/prototype) -> gilgamesh's_master_(fate/prototype)
rename arjuna_(fate/grand_order) -> arjuna_(fate)
rename arjuna_alter -> arjuna_(alter)_(fate)
rename arondight -> arondight_(fate)
rename artemis_(fate/grand_order) -> artemis_(fate)
rename arthur_pendragon_alter_(fate) -> arthur_pendragon_(alter)_(fate)
rename ashwatthama_(fate/grand_order) -> ashwatthama_(fate)
rename assassin_(fate/stay_night) -> sasaki_kojirou_(fate)
rename assassin_class_(fate/stay_night) -> assassin_class_(fate)
rename asterios_(fate/grand_order) -> asterios_(fate)
rename astraea_(fate/grand_order) -> astraea_(fate)
rename avalon_(fate/stay_night) -> avalon_(fate)
rename avenger -> angra_mainyu_(fate)
rename avenger_class_(fate/stay_night) -> avenger_class_(fate)
rename balmung_(fate/apocrypha) -> balmung_(fate)
rename bartholomew_roberts_(fate/grand_order) -> bartholomew_roberts_(fate)
rename bedivere -> bedivere_(fate)
rename bellerophon -> bellerophon_(fate)
rename benienma_(fate/grand_order) -> benienma_(fate)
rename beowulf_(fate/grand_order) -> beowulf_(fate)
rename berserker -> heracles_(fate)
rename berserker_(fate/strange_fake) -> jack_the_ripper_(fate/strange_fake)
rename berserker_class_(fate/stay_night) -> berserker_class_(fate)
rename billy_the_kid_(fate/grand_order) -> billy_the_kid_(fate)
rename black_keys -> black_keys_(fate)
rename boudica_(fate/grand_order) -> boudica_(fate)
rename bradamante_(fate/grand_order) -> bradamante_(fate)
rename bucephalus -> bucephalus_(fate)
rename caladbolg -> caladbolg_(fate)
rename calamity_jane_(fate/grand_order) -> calamity_jane_(fate)
rename caliburn -> caliburn_(fate)
rename caligula_(fate/grand_order) -> caligula_(fate)
rename captain_nemo_(fate/grand_order) -> captain_nemo_(fate)
rename carmilla_(fate/grand_order) -> carmilla_(fate)
rename caster -> medea_(fate)
rename caster_lily -> medea_(lily)_(fate)
rename caster_(fate/strange_fake) -> alexandre_dumas_(fate)
rename caster_(fate/zero) -> gilles_de_rais_(fate/zero)
rename caster_class_(fate/stay_night) -> caster_class_(fate)
rename castor_(fate/grand_order) -> castor_(fate)
BUR – RENAME Ch – G (50 tags)
rename chacha_(fate/grand_order) -> chacha_(fate)
rename charles_babbage_(fate/grand_order) -> charles_babbage_(fate)
rename charles_henri_sanson_(fate/grand_order) -> charles-henri_sanson_(fate)
rename charlotte_corday_(fate/grand_order) -> charlotte_corday_(fate)
rename chevalier_d'eon_(fate/grand_order) -> chevalier_d’eon_(fate)
rename child_gilgamesh -> child_gilgamesh_(fate)
rename christopher_columbus_(fate/grand_order) -> christopher_columbus_(fate)
rename circe_(fate/grand_order) -> circe_(fate)
rename clarent -> clarent_(fate)
rename cleopatra_(fate/grand_order) -> cleopatra_(fate)
rename colonel_olcott_(fate/grand_order) -> colonel_olcott_(fate)
rename cu_chulainn_(fate/grand_order) -> cu_chulainn_(caster)_(fate)
rename cu_chulainn_alter_(fate/grand_order) -> cu_chulainn_(alter)_(fate)
rename dahut_(fate/grand_order) -> dahut_(fate)
rename darius_iii_(fate/grand_order) -> darius_iii_(fate)
rename david_(fate/grand_order) -> david_(fate)
rename demeter_(fate/grand_order) -> demeter_(fate)
rename demon_pillar_(fate/grand_order) -> demon_pillar_(fate)
rename dun_stallion -> dun_stallion_(fate)
rename ea_(fate/stay_night) -> ea_(fate)
rename edmond_dantes_(fate/grand_order) -> edmond_dantes_(fate)
rename edward_teach_(fate/grand_order) -> edward_teach_(fate)
rename elixir_of_love_(fate/grand_order) -> elixir_of_love_(fate)
rename emiya_alter -> emiya_(alter)_(fate)
rename enki_(fate/prototype) -> enki_(fate)
rename enkidu_(fate/strange_fake) -> enkidu_(fate)
rename enkidu_(weapon) -> enkidu_(weapon)_(fate)
rename ereshkigal_(fate/grand_order) -> ereshkigal_(fate)
rename eric_bloodaxe_(fate/grand_order) -> eric_bloodaxe_(fate)
rename europa_(fate/grand_order) -> europa_(fate)
rename euryale -> euryale_(fate)
rename excalibur -> excalibur_(fate/stay_night)
rename excalibur_morgan -> excalibur_morgan_(fate)
rename excalibur_galatine -> excalibur_galatine_(fate)
rename fergus_mac_roich_(fate/grand_order) -> fergus_mac_roich_(fate)
rename fergus_mac_roich_(young)_(fate/grand_order) -> fergus_mac_roich_(young)_(fate)
rename florence_nightingale_(fate/grand_order) -> florence_nightingale_(fate)
rename florence_nightingale_santa_(fate/grand_order) -> florence_nightingale_(santa)_(fate)
rename fou_(fate/grand_order) -> fou_(fate)
rename fragarach -> fragarach_(fate)
rename fuuma_kotarou_(fate/grand_order) -> fuuma_kotarou_(fate)
rename gae_bolg -> gae_bolg_(fate)
rename galahad_alter -> galahad_(alter)_(fate)
rename gareth_(fate/grand_order) -> gareth_(fate)
rename gawain_(fate/extra) -> gawain_(fate)
rename gazer_(fate/grand_order) -> gazer_(fate)
rename geronimo_(fate/grand_order) -> geronimo_(fate)
rename gilgamesh -> gilgamesh_(fate/stay_night)
rename goetia_(fate/grand_order) -> goetia_(fate)
rename grainne -> grainne_(fate)
BUR – RENAME H – L (44 tags)
rename han_xin_(fate/grand_order) -> han_xin_(fate)
rename hans_christian_andersen_(fate)_(adult) -> hans_christian_andersen_(adult)_(fate)
rename hector_(fate/grand_order) -> hector_(fate)
rename helena_blavatsky_(fate/grand_order) -> helena_blavatsky_(fate)
rename hessian_(fate/grand_order) -> hessian_(fate)
rename hijikata_toshizou_(fate/grand_order) -> hijikata_toshizou_(fate)
rename houzouin_inshun_(fate/grand_order) -> houzouin_inshun_(fate)
rename ibaraki_douji_(fate/grand_order) -> ibaraki_douji_(fate)
rename ifrit_(fate/grand_order) -> efreet_(fate)
rename invisible_air -> invisible_air_(fate)
rename ishtar_(fate/grand_order) -> ishtar_(fate)
rename ivan_the_terrible_(fate/grand_order) -> ivan_the_terrible_(fate)
rename jaguarman_(fate/grand_order) -> jaguarman_(fate)
rename james_moriarty_(fate/grand_order) -> james_moriarty_(fate)
rename jason_(fate/grand_order) -> jason_(fate)
rename jeanne_d'arc_(swimsuit_archer) -> jeanne_d'arc_(swimsuit_archer)_(fate)
rename jeanne_d'arc_(alter_swimsuit_berserker) -> jeanne_d'arc_(alter_swimsuit_berserker)_(fate)
rename jing_ke_(fate/grand_order) -> jing_ke_(fate)
rename joyeuse_ordre -> joyeuse_ordre_(fate)
rename julius_caesar_(fate/grand_order) -> julius_caesar_(fate)
rename kama_(fate/grand_order) -> kama_(fate)
rename karin_(fate/requiem) -> karin_(fate)
rename katsushika_hokusai_(fate/grand_order) -> katsushika_hokusai_(fate)
rename kasuga_no_tsubone_(fate/grand_order) -> kasuga_no_tsubone_(fate)
rename katou_danzou_(fate/grand_order) -> katou_danzou_(fate)
rename king_hassan_(fate/grand_order) -> king_hassan_(fate)
rename kiyohime_(fate/grand_order) -> kiyohime_(fate)
rename kobayashi_(fate/zero) -> kobayashi_(fate)
rename kotone_(fate/zero) -> kotone_(fate)
rename koyanskaya -> koyanskaya_(fate)
rename lahmu -> lahmu_(fate)
rename lakshmibai_(fate/grand_order) -> lakshmibai_(fate)
rename lancer -> cu_chulainn_(fate/stay_night)
rename lancer_(prisma_illya) -> cu_chulainn_(fate/kaleid_liner)
rename lancer_class_(fate/stay_night) -> lancer_class_(fate)
rename lavinia_whateley_(fate/grand_order) -> lavinia_whateley_(fate)
rename leonardo_da_vinci_(fate/grand_order) -> leonardo_da_vinci_(fate)
rename leonidas_(fate/grand_order) -> leonidas_(fate)
rename leysritt -> leysritt_(fate)
rename li_shuwen_(fate/grand_order) -> li_shuwen_(young_lancer)_(fate)
rename li_shuwen_(koha-ace) -> li_shuwen_(old_lancer)_(fate)
rename li_shuwen_(fate) -> li_shuwen_(young_assassin)_(fate)
rename imperial_head_guard_(fate/grand_order) -> li_shuwen_(old_assassin)_(fate)
rename lobo_(fate/grand_order) -> lobo_(fate)
BUR – RENAME M – Q (46 tags)
rename mandricardo_(fate/grand_order) -> mandricardo_(fate)
rename marie_antoinette_(fate/grand_order) -> marie_antoinette_(fate)
rename marie_antoinette_(alter)_(fate/grand_order) -> marie_antoinette_(alter)_(fate)
rename mary_read_(fate/grand_order) -> mary_read_(fate)
rename mata_hari_(fate/grand_order) -> mata_hari_(fate)
rename matsudaira_nobutsuna_(fate/grand_order) -> matsudaira_nobutsuna_(fate)
rename medjed -> medjed_(fate)
rename medusa_(lancer_alter)_(fate) -> medusa_(alter)_(fate/grand_order:_first_order)
rename mephistopheles_(fate/grand_order) -> mephistopheles_(fate)
rename merlin_(fate) -> merlin_(fate/stay_night)
rename minamoto_no_raikou_(fate/grand_order) -> minamoto_no_raikou_(fate)
rename mithrenes -> mithrenes_(fate)
rename miyamoto_musashi_(fate/grand_order) -> miyamoto_musashi_(fate)
rename mochizuki_chiyome_(fate/grand_order) -> mochizuki_chiyome_(fate)
rename moses_(fate/prototype_fragments) -> moses_(fate)
rename musashibo_benkei_(fate/grand_order) -> musashibo_benkei_(fate)
rename mysterious_heroine_x -> mysterious_heroine_x_(fate)
rename mysterious_heroine_x_(alter) -> mysterious_heroine_x_(alter)_(fate)
rename mysterious_heroine_xx_(foreigner) -> mysterious_heroine_xx_(fate)
rename naga_(fate/grand_order) -> naga_(fate)
rename nameless_dagger -> nameless_dagger_(fate)
rename napoleon_bonaparte_(fate/grand_order) -> napoleon_bonaparte_(fate)
rename nefertari_(fate/prototype_fragments) -> nefertari_(fate)
rename nezha_(fate/grand_order) -> nezha_(fate)
rename nikola_tesla_(fate/grand_order) -> nikola_tesla_(fate)
rename nitocris_(fate/grand_order) -> nitocris_(fate)
rename nursery_rhyme_(fate/extra) -> nursery_rhyme_(fate)
rename oda_nobukatsu_(fate/grand_order) -> oda_nobukatsu_(fate)
rename odysseus_(fate/grand_order) -> odysseus_(fate)
rename okada_izou_(dog) -> okada_izou_(dog)_(fate)
rename onui_(fate/grand_order) -> onui_(fate)
rename oprichnik_(fate/grand_order) -> oprichnik_(fate)
rename orion_(fate/grand_order) -> orion_(bear)_(fate)
rename osakabe-hime_(fate/grand_order) -> osakabe-hime_(fate)
rename ougi_(fate/zero) -> ougi_(fate)
rename paris_(fate/grand_order) -> paris_(fate)
rename parvati_(fate/grand_order) -> parvati_(fate)
rename patxi -> patxi_(fate)
rename paul_bunyan_(fate/grand_order) -> paul_bunyan_(fate)
rename penthesilea_(fate/grand_order) -> penthesilea_(fate)
rename phantom_of_the_opera_(fate/grand_order) -> phantom_of_the_opera_(fate)
rename photon_ray -> photon_ray_(fate)
rename pollux_(fate/grand_order) -> pollux_(fate)
rename qin_shi_huang_(fate/grand_order) -> qin_shi_huang_(fate)
rename queen_of_sheba_(fate/grand_order) -> queen_of_sheba_(fate)
rename quetzalcoatl_(fate/grand_order) -> quetzalcoatl_(fate)
BUR – RENAME R & S (40 tags)
rename rama_(fate/grand_order) -> rama_(fate)
rename rasputin_(fate/grand_order) -> rasputin_(fate)
rename red_hare_(fate/grand_order) -> red_hare_(fate)
rename rider_(fate/strange_fake) -> pale_rider_(fate)
rename rider_class_(fate/stay_night) -> rider_class_(fate)
rename rhongomyniad -> rhongomyniad_(fate)
rename roland_(fate/grand_order) -> roland_(fate)
rename rohngall -> rohngall_(fate)
rename romulus_(fate/grand_order) -> romulus_(fate)
rename romulus_quirinus_(fate/grand_order) -> romulus_quirinus_(fate)
rename saber_(fate/strange_fake) -> richard_i_(fate)
rename saber_class_(fate/stay_night) -> saber_class_(fate)
rename saint_george_(fate/grand_order) -> georgios_(fate)
remove implication saint_martha_(swimsuit_ruler)_(fate) -> saint_martha
rename saint_martha -> martha_(fate)
rename saint_martha_(swimsuit_ruler)_(fate) -> martha_(swimsuit_ruler)_(fate)
rename sakata_kintoki_(fate/grand_order) -> sakata_kintoki_(fate)
rename sakata_kintoki_rider_(fate/grand_order) -> sakata_kintoki_(rider)_(fate)
rename salome_(fate/grand_order) -> salome_(fate)
rename saver -> saver_(fate/prototype)
rename scathach_skadi_(fate/grand_order) -> scathach_skadi_(fate)
rename scheherazade_(fate/grand_order) -> scheherazade_(fate)
rename sella -> sella_(fate)
rename sengo_muramasa_(fate) -> senji_muramasa_(fate)
rename shamhat -> shamhat_(fate)
rename sherlock_holmes_(fate/grand_order) -> sherlock_holmes_(fate)
rename shibata_katsuie_(fate/grand_order) -> shibata_katsuie_(fate)
rename shirley_(fate/zero) -> shirley_(fate)
rename shuten_douji_(fate/grand_order) -> shuten_douji_(fate)
rename siduri_(fate/grand_order) -> siduri_(fate)
rename sieg_(fate/apocrypha) -> sieg_(fate)
rename sigma_(fate/strange_fake) -> sigma_(fate)
rename sigurd_(fate/grand_order) -> sigurd_(fate)
rename sita_(fate/grand_order) -> sita_(fate)
rename sitonai -> sitonai_(fate)
rename solomon_(fate/grand_order) -> solomon_(fate)
rename spriggan_(fate/grand_order) -> spriggan_(fate)
rename stheno -> stheno_(fate)
rename summer_casual_(fate/grand_order) -> summer_casual_(fate)
rename surtr_(fate/grand_order) -> surtr_(fate)
BUR – RENAME T – Z (32 tags)
rename tanaka_(fate/kaleid_liner) -> tanaka_(fate)
rename tasuke_(fate/grand_order) -> tasuke_(fate)
rename tawara_touta_(fate/grand_order) -> tawara_touta_(fate)
rename thomas_edison_(fate/grand_order) -> thomas_edison_(fate)
rename tiamat_(fate/grand_order) -> tiamat_(fate)
rename tristan_(fate/grand_order) -> tristan_(fate)
rename true_assassin -> hassan_of_cursed_arm_(fate)
rename true_caster -> francois_prelati_(fate)
rename true_rider -> hippolyta_(fate)
rename tokitarou_(fate/grand_order) -> tokitarou_(fate)
rename tomoe_gozen_(fate/grand_order) -> tomoe_gozen_(fate)
rename tool_(fate/apocrypha) -> toole_(fate)
rename toyotomi_hideyoshi_(koha-ace) -> toyotomi_hideyoshi_(fate)
rename twinmyniad -> twinmyniad_(fate)
rename valkyrie_(fate/grand_order) -> valkyrie_(fate)
rename ortlinde_(fate/grand_order) -> ortlinde_(fate)
rename hildr_(fate/grand_order) -> hildr_(fate)
rename thrud_(fate/grand_order) -> thrud_(fate)
rename trimmau -> trimmau_(fate)
rename violet_(fate/extra_ccc) -> violet_(fate)
rename viy -> viy_(fate)
rename voyager_(fate/requiem) -> voyager_(fate)
rename watcher_(fate/strange_fake) -> watcher_(fate)
rename william_tell_(fate/grand_order) -> william_tell_(fate)
rename wolfgang_amadeus_mozart_(fate/grand_order) -> wolfgang_amadeus_mozart_(fate)
rename wu_zetian_(fate/grand_order) -> wu_zetian_(fate)
rename xiang_yu_(fate/grand_order) -> xiang_yu_(fate)
rename xuanzang_(fate/grand_order) -> xuangzang_sanzang_(fate)
rename yagyuu_munenori_(fate/grand_order) -> yagyuu_munenori_(fate)
rename yan_qing_(fate/grand_order) -> yan_qing_(fate)
rename yang_guifei_(fate/grand_order) -> yang_guifei_(fate)