Awsome, hopefully the mass platform online games (such as Madden) won't be limited with the online play. They should have it all together by now.
Ya, probobly just avatar Miis. Kind of like XBL with the accounts that store user-specific date. Same thing here.
A cheat-code to use Miis would be cool though, even if the heads were just paisted on the bodys will a few animations.