So after consideration, I decided that I'd be find with either a Harem ending or a Sayuki victory
Consider:
Sayuki and Yukia are like a strong base and a strong acid respectively. If you have both of them, they'll mellow each other's excessive tendencies out and add balance to the situation. So instead of having to invest in BDSM gear, he can live comfortably in the knowledge he's safe from their more...dangerous...desires.
Mizhua is probably Cinderella given
she's an exhibitionist and she would have the most access and knowledge of her brother and the means to do so. She's also implied to be a brocon, so there's motive.
She'd probably be best to help keep everyone grounded and help with domestic life when he's trying to wrangle the cats.
Fujoshi girl would just kinda be there because tsundere
If all else fails, Sayuki will probably get him in the least amount of legal trouble while also giving him the least amount of physical or emotional harm, so she'd be good for that