I think there already is a method to make one of your slaves more dominant. It was implemented times ago as an essential part of the infamous
"legacy edition". It was called
marriage, and at least in my game it succeeded to turn one nice and pleasant slave girl into a total bitch, so high and mighty she demanded all of my MC:s attention, time and preferably also the money as well.
Not to
recommend marital life really - alimony sucks - but the option of marriage should still be there and lately the GD studios mentioned that the wife has got more interactions than the slaves, methinks. Even a brief experimenting with marriage was enough to completely heal my severe addiction towards this game. (
Such a bad experience. Never again!)