The other concept is if you completely get rid of divisions altogether. Right now, some of the biggest points of contention in all of the conferences is that you have to stack divisions to keep rivalries together, but it screws up the competitive balance of the league.
For example, the Pac 12 has a screwy schedule because even though they put Stanford and Cal in the North division, they still have to play USC and UCLA every single year. It screws up any sort of fair rotation.
In the Big Ten, Michigan, Ohio State, and Michigan State are all in the same division. That's stupid. Wisconsin is running roughshod all over the western division, or whatever stupid thing they're calling it now.
The ACC screws themselves because Florida State plays Clemson every year, and then that means the winner has to play Georgia Tech or Duke in the ACC title game making for, typically, horrendous football.
The NCAA is the one mandating that you have to have divisions. There's really no need for them, to be honest. You could get more creative with your scheduling if you could simply do away with them.