Rin x Molly, Ayane x Yasu, and Definitely Maya x Noriko are going to be very interesting.
What I'm hoping for:
Yumi x Tsuneyo in a Kendo battle. Yakuza Princess vs Flavour Samurai. If not that then friendzone battle.
Chika x Uta in a Caretaker battle. Sensei has to decide who would be a better caretaker.
Ayane x Yasu in a Karaoke battle. Don't know how, but Yasu saying Ayane wants to replace Maya will probably come up.
Sana x Otoha in a Little Sister to Sensei battle. Fucked up, I know. Either that or a music battle. Drum vs Vocals. Not sure how that'd work though. Could also see the Date battle here.
Makoto x Kirin in a Date battle? Seems to fit how their stories are going. If not Date battle then probably like a pervert quiz or something. Who knows more about sex etc.
Miku x Io... Not sure on this one. Scary Room? Fits the anxiety pill stuff.
Rin x Molly in a Cosplay battle. Maybe even have to pretend to be the other. Could also see the Date battle here or simply a gamer girl fight.
Futaba x Nodoka in a Better poetry battle.
Ami x Touka in a Cooking battle. Can't really think of anything else. Also this'll give Ami access to weapons. Could also see them competing over who would be a better mother. Maybe even a popularity contest? That would probably bring out Psycho Ami.
Maya x Noriko in a Who knows Sensei better battle. Except Yasu gets to ask the questions since she won last time. (Probably won't happen but it'd be so interesting.)