Personally, I'd go for the physics. The game's got decent character variation as it is, sure there is room for improvement but the one aspect that screams "outdated" is the sexual interaction. The facial expressions, sounds and new animations did a lot to improve it, but the bread and butter of sex (aka penetration) is still 2 models clipping into each other; also breasts have only one motion. What would be awesome is a system that keeps the penis aligned with the chosen hole regardless of the position and stretches the hole according to size (maybe this would allow players to switch the type of penetration vaginal/anal during any position or just the ones in which the movement would be natural both ways). Add to that better breasts, hair and cloth physics and the sex scenes will fully come to life. Since sex is a central component of the game, I think this would make for a much more appreciated overhaul.
As for the character variation, the way I see it, you could improve it bit by bit through the monthly updates AND still have the physics overhaul. This month is the tattoos, next could be ethnicity features, then genital update (different types of editable pussies and more variation to male penises or at least have them share the same customization options as the shemales) and so on. There kink of the month updates would make sure too keep the scene sector fresh while the other updates could enrich the customization.
(*
shemales, ehh, you mean Futa, right ?)
Also, the Futa need to have some 'shared' sex animations with the males !
Often, you'll get an scene, that is a 3-some, your Futa, and two females . Since, the Futa has a Penis, they should have access, to the same male animation penetration positions, as the males have, and also the girl-on-girl animations !
But, more often, than not, you get the message, " There are no animations available for this character "
. Really, that's not actually true, they just haven't been
linked correctly/properly.
Then, when there is a 'gang-bang' scene, with the Futa, a male, and 3 females;
the Futa, is treated as a Female only, even though she has a Dick, and can assist the other Male, in fucking the 3 females, AND also be fucked by the Male, AND even include some girl-on-girl action !
Now that'd be a great Gang-Bang Action Scene ! (if, only things were
linked correctly/properly, to happen that way )