The thing is, a female Custodian is entirely possible within lore, as the argument against them is based on a flawed assumption.
"There can't be female Space Marines!"
Leaving aside that Guilliman opening the Emperor's old research archives and being able to create the Primaris Marines shows there were always more improvements possible for the Astartes, which may possibly one day include being able to enact their creative process on women, people who shout that like it's some protective mantra forget one crucial thing.
Custodes are not Astartes.
They are entirely different beings, born of an entirely different process. If you were to get a chance to look inside a Custodian, you would not find those intriguing additional organs or other modifications which you would see within an Astartes. You would find the same internal organs as an ordinary human has, albeit scaled up to the size of the person whose body they were in, and operating at peak efficiency at all times.
Because they are not Astartes, they are not bound by the same canon restrictions. Sorry, neckbeards.
I was getting Rikako vibes as well, so I thought I'd shoot a DM at the commissioner to see if I could get a more definitive answer, and it is indeed Rikako according to them.
