The easiest thing the BIG can do would be to pair the 4 western-most teams (Nebraska, Minny, Iowa & Wisco) with the 3 eastern-most teams (PSU, Rutgers, Maryland). The teams from Illinois, Indiana, Michigan & Ohio are the other division.
All natural rivalries remain intact. Iowa's division would feature 2 "blue-bloods" in PSU and Nebraska, and 2 teams that have shown they can compete for conference titles (Wisco & Iowa). The other division would have 2 "blue bloods" in Ohio State & Michigan and 2 teams that have shown they can compete for conference titles in Mich St and Northwestern.