idea: make it so if your cock is too big the person your mating with could go braindead only a 50 % survival rate but the survivors are mentally braindead and unfunctional and well need diaps well it is realistic
or, if you make everything too big, your character is immobile and has to get around via wheelchair bc too big boob, dick, or balls. though, that would be stupid since 90% of the games functions rely on mobility.