Jon I've been looking at possible solutions other then Illinois switching divisions and this is the best solution. If you swapped Illinois/Wisconsin/Purdue for Michigan/Michigan State. Their would be basically no need for crossover games anymore which would make rotation of non-division games alot easier and you'd see more teams more often. If the divisions were
Wisconsin
Iowa
Nebraska
Northwestern
Illinois
Purdue
Minnesota
OSU
Michigan
Penn state
Michigan state
Indiana
Rutgers
Maryland
The only trophy games if you didnt' have crossover games would be Purdue/Indiana which is basketball rival nobody cares about it in football and Minn/Michigan was a rivalry 50 years ago and Minnesota values Iowa/Wisconsin more and Michigan values OSU/MSU more so basically its both teams 3rd biggest if even that.
This also takes care of the problem that hasn't happened yet, but eventually will of Mich/OSU playing each other back to back weeks in big ten championship. Wisconsin and Iowa get to play each other and really the rivalry that may be becoming bigger is Nebraska and Wisconsin.
You still have 3 powers on both sides of the table, but with Penn state eventual decline having the 2 main powers on one side isn't as big of problem especially with Wisconsin becoming big power in the big ten. You could easily do this and by the time Penn state has returned to power we will probably expand to 16 teams and you reevaluate the divisions at that point. I think it makes the most sense for everyone and we could even see more teams from the non-division a lot more without crossover rivals.
Purdue is technically more west then Indiana it makes complete geographical sense and you changed the division names to east/west and be done with it.
EDIT: You lose those 2 trophy games of Minn/Mich, Indy/purdue, but gain 2 back of Iowa/Wis and PSU/MSU