I'd suggest three divisions, based on their traditional strengths:
None of the Above
In football, play the normal round robin schedule, but only have the four in the football division play teams in the other divisions, with Ohio State vs. Michigan and Penn State vs. Nebraska being the season ending games, also serving as semi-finals for the Big Ten championship game. You are virtually assured of getting at least two teams in the BCS every year that way. Nevermind the pesky Wisconsin problem. If Wisconsin goes undefeated, you can have them make the BCS or NC game anyway, right?
Also, you could have relegation. If one team is super great at football from one of the other divisions, just substitute them for Michigan, which is the sux in football anyway. Once Michigan
For basketball, it doesn't really matter what the regular season entails, because OMG!1!1 tornament!!!!! chooses the trueliest true champion. For other sports, just have your normal schedule, except for wrasslin', which is statutorily won by Iowa or Nebraska every year, and baseball, which should be abolished because you can't play at home until May.
Look, if the Big Ten wants to keep the two team BCS gravy train up, this is a golden opportunity to do so. If you aren't going to let pesky things like geography get in the way of naming divisions, don't waste an opportunity to ensure you get what you want out of snagging Nebraska.