I was wondering, is it possible to keep the game from switching a male slave's pronouns to female after you give them a vagina, or does it consider all characters with a vagina as female?
It is definitely possible. However it might take quite a bit of fidgeting in the code. i've looked around some and the way i see it there two genders in current pronoun coding (in the game there are 3, but bear with me here). There's a male and there's not male, so basically futanari has female pronouns because it is not a male.
Now to achieve what you want you could change it around. So everything that IS female will have female pronouns and everything else will have male. If you really want to test it out i can give you pointers what might work according to me and it will be up to you to test it ;]
Of course I might be totally wrong and there might be a much easier way, or my way will totally botch things up. I've only started to mess with s4p so i don't claim i have full understanding of scripts here.
The game does not track birth sex, nor gender(though the term appears in some parts of the code, it still means sex). You would need to add one of those functionalities to achieve the effect of referring to trans-sexual slaves by alternate pronouns. Also, unless you added save file correction code or manually updated them, the changes would not be compatible with existing save files.
I've only changed part of coding in person.gb so the futanari is referred to as a male in some sentences and as a female in others. As you can see below it is entirely possible and probably wont take all that much work.
