I think the best twist is that Monica is the third beneficiary, and she only gets the money if you somehow don't meet the conditions to get it (like staying with Monica, Katie or Jenna). This way, Monica could even incite Jenna and or Katie to seduce you (if she fails) so you lose the money and she keeps it (Katie and Jenna could not even know about the will conditions, other than what you have told them).
Maybe Jolina / Bella being the third party is also possible (and more likely) but I think the best twist, as most peoples favorite girls are Katie, Jenna or Monica would be for them to be evil (or Monica at least).
As long as Lily is free of guilt and I can bang her up, I will live happily ever after. And please, for the love of God, can we have a bit of a pregnant Lily ?, I think my life would be complete after that. (I am not a patron, but if being a patron can make this happen, please one of the devs DM me and I will put my money where my heart is).