The Japanese really are fond of adding breasts to traps. Tieria_erde is one example, miyanokouji_mizuho has his share, and akizuki_ryou has his share of pics with breasts too. But then, what does that make them? Are they still traps, just traps with breasts? Or are they newhalfs? Or we count them as genderswaps like so often seems to be tagged?
Personally, I say;
known trap + breasts, can't see genitals = label as newhalf
known trap + breasts, can see only cock = label as newhalf
known trap + breasts, can see pussy & cock = label as futanari
known trap + breasts, can see only pussy = label as just genderswap since there's no female tag.
Point is, first take the known information on the character then change it based on what you see. This should be how things already work I'd think. I mean, if a known trap isn't dressed up as a girl and appears obviously male, would you still tag them as a trap? I would assume not.