At this point, it would seem the only people in favor of simple geography-based divisions are (1) Penn State fans and (2) me.
The latest division proposal comes from the generally highly reasonable and eminently well-informed Stewart Mandel. He advocates sending Northwestern to the East in place of Penn State. Using win-loss data going back to 1993 (the year Penn State joined the Big Ten), he asserts this creates two perfectly-balance divisions. That's true on a total-ranking basis, but not on a distributional basis. The East would have the top two teams over the last 17 seasons in Ohio State and Michigan to go with four teams who rank in the bottom six over that time period. The West meanwhile has four of the six traditional upper-division teams.
So the fundamental question here is something like, "Are you willing to put 4 of the top 6 teams in one division to avoid having 3 of the top 4 in the other?" My take is that the first danger has a greater probability of occurring than the second--and that, all things being equal, going with geography and the maximum number of maintained annual rivalries is the way to go--but the math basically boils down to what you prognosticate about Michigan's future, and maybe I'm not an unbiased observer there.
Anyway, I'm ready to concede. The proposals to send Penn State out west and move Illinois, Northwestern, or (to a lesser extent) Wisconsin to the east certainly look to be in MSU's best interests. If it's one of the Illinois schools moving to the east, MSU suddenly looks like a good bet to be the #3 team in the division over time--#2 is you believe we can help keep our friends in Ann Arbor down for a few more years. TOC Twitter follower Mike Tierney notes that MSU would have been in contention to make the 2008 conference championship game under Mandel's divisional set-up. (Of course, that set-up also look a lot like giving Ohio State an automatic bid in the conference championship game until whatever time Michigan returns to glory.)
Based on Adam Rittenberg's tweets today reporting Purdue AD Morgan Burke's comments on the likely division-related thinking of Big Ten leaders, it certainly sounds like the smart bet is on Penn State heading out west to join Nebraska, breaking up the four traditional powers based on multi-decade results. (Note: Using a 50-year timeframe, as Burke's comments suggest, is clearly part of a conspiracy to hold down MSU by ignoring our glory years in the 1950's. [Note: Not really.])
We give. Send the Nittany Lions out west to battle the Plains State powers. We'll hang back east and see if we can't make a run at the top from time to time.
P.S. Completely unrelated: I'm a little late on this, but how cool does the van Tom Izzo uses for Midwest recruiting trips sound? The Recruit Baggin' Wagon.