Adding in different enemies would be nice, possbily in a whole other area after defeating the bunny girl. also making the game a bit of a rouge light might be fun with permanent upgrades, but that might work against the save files.
also adding in some possible dom skills for Quinton once he gains a large amount of curruption. you could have him just learn how to 'drain' the girls and have the main debuffs be less stats because he's filled up or covered in cum.
something else is potions for body modifications to help quinton please the girls a bit more. something like adding breasts or making his dick bigger. this would make it possible for him to be more dominante once you get a larger penis potion. it could last for a few seconds and we could get some scenes were He gets back at the girls for a bit before changing back.