For the "dominatrix stuff", somehow you can already play a femdom game with the good settings. If you choose only female friends with very low friendship, they will more likely be mean and unfair with you in the challenges (harder slaps, will make you beg, harsher reactions, etc).
I want to allow the players to create their own "scenario" when modifying the settings and customizing the friends. Of course it's not perfect for the moment, and it will never be, but I'll try to improve it over time.
As for JOI, I think it can match with a challenge pretty good!