Not really a fan of either of the three, but if it's between them, I think I'd go for Mandana.
Mandana is a selfish asshole who constantly plays the victim card (crying, saying someone is sexist, pulling out racism card, etc.) while acting like a hypocrite and constantly breaking rules (speaking english, violence, taking off mike for no reason, etc.). But besides that, she's remained consistent throughout the show. She hasn't really changed her game on someone's persistence or feedback and she hasn't claimed to be something she's not. She's continually admitted on the show that she isn't here to make friends and that she's playing to win. So I'd rather it be her than the others.
If it's not Mandana, according to the scenario, then I'd want Rishabh. While I think he gets influenced too many and changes his game too much according to views, he does attempt to play the game and he does have some smarts. Plus, as you (TM) pointed out, his entry definitely added some life into the show. If there was ever a wildcard who deserved to win, I'd have to say it was him.
Under no circumstances do I want Prince. Although he has the biggest fan group and although he has the highest chances of winning, I think Prince is the most undeserving winner. He literally is so dumb its unfair for make him the winner. No real idea of the game or anything. All he's good at, is being influenced by others and going according to them (First Kishwar, then his sister, then Rochelle, then Kishwar again, then Nora, and now a mix), and tasks. Not to mention, he can be a downright asshole to people and still attempts to claim himself as the one with morals. Not a fan of him. He's funny and probably is a good friend, but I don't think he deserves to win BB.