[@Eklispe] Sorry for the holdup, some communication hiccups between me and Sat made me unwilling to answer any sooner.

So to your first question, the characters [i]themselves[/i] decide who teams up with who. If your cast gets along well with my cast, for example, there's a real chance they'd decide to team up. The same applies to anyone looking to ally with Satoshi's crew. Conversely, I doubt the Synchro or Water dorm would team up, considering they showed hostility to each other so far.

To answer the second, I don't recommend trying it. You can be a sneaky snitch and do it anyway, but if either dorm found out you're attempting to double-time them, I doubt they'd want to be your ally for much longer.