I also haven't played the Hope's Peak AU bonus thing in a while, buuuut I recall it being a pretty straightforward thing. And honestly just a typical flavor high school AU works just fine for me.

Except, you know, I really like the idea of them being rival assassins. So they could both end up undercover at the school? If you want to get plotty we could come up with some sort of reason that they're both there. Maybe a long-term mission where they have to work together to take out target(s) nearby, or even target someone who works at the school.

We could also slip into hurt/comfort really easily, if one or both of them messes something up. Just spitballing, though!