If the B1G added ISU and KU and needed four 4-team pods it would be very interesting to see how they shook out.
Michigan and Ohio State have to be together; Michigan State has to be in this one too. Is Penn State team #4, or is that too loaded?
Minnesota, Wisconsin, and Iowa is another obvious group of three. Nebraska probably would want in here, but then you are killing the Cy-Hawk, which is one of the more fun and compelling rivalries that you just added to your own conference. On the other hand, if you add ISU in here, you're probably left with a Nebraska/Kansas/Illinois/Northwestern pod.
And of course none of the "have to be together" teams actually have to be if there is some form of protected rivalry.
Maybe you do pure geography and fix it on the back-end with protected rivals (in parenthesis when obvious):
West
Nebraska
Kansas
Iowa (Minnesota)
Iowa State
North
Minnesota (Iowa)
Wisconsin
Illinois
Northwestern
Central
Indiana
Purdue
Michigan (Ohio State)
Michigan State
East
Ohio State (Michigan)
Penn State
Maryland
Rutgers