I personally feel this isn't really the right way to take things at all - just adding more and more girls.
Right now, you have 4 girls that may have distinctive looks, but they play out all the same. The activities and interactions are all the same (if with different poses) and each girl behaves all-around the same with them, with very little in variation when it comes to that. I feel it could be fleshed out way more by giving each character certain interactions, activities to do or lewd acts exclusive to them in order for it to feel a bit more specialized.
As it stands, they feel more or less like cardboard cutouts with little personality, which is something that always bugged me in this game in particular.
100% this, the only original girl in the game is Rogue because of her addiction stat.
Otherwise they are copy paste cardboard cutouts with minor dialogue changes that suggest the same relationship types when reaching the same stats. You can all make them submissive exhibitionists or loving girlfriends the same way. It would be more interesting if for instance Laura or Emma would resist a certain stat (exhibition or submissiveness). Personally I would think they would have more dominant personalities due to their mutation.
Especially the expanded MOD people that added Mystique should not make her submissive
Disclaimer: I have only watched the X-men movies so I know very little of the universe portrayed in the original comics and TV shows
Also another thing that could be added i.s.o. another girl is graphics and animations.
Threesomes are currently text only, same with the biology note of Rogue in class, showering with two girl that rub on you is just a zoom in which works for one girl but looks awkward when its two ...