That's where you start to argue more geographic and less historic. Do you put LSU and Mississippi St there and then shift around virtually all the other divisions as well to accommodate that switch? If trying to keep historical teams I could see what Japan Coug said above about keeping Iowa in the Big Ten, shifting Penn St to the Big East group, and putting Louisville with the Big 12 schools. If it was done strictly geographically without regard to historical ties then I could see things something like this:

Northeast:
Boston College
Syracuse
Rutgers
Penn St
Pittsburgh
Ohio St
West Virginia
Maryland
Virginia Tech
Virginia

Mid-Atlantic:
Wake Forest
Duke
North Carolina
NC State
Kentucky
Louisville
Cincinnati
Tennessee
Vanderbilt
Clemson

Southeast:
South Carolina
Georgia
Georgia Tech
Florida
Florida St
UCF
Miami FL
Alabama
Auburn
Mississippi St

Great Lakes:
Michigan
Michigan St
Indiana
Purdue
Notre Dame
Illinois
Northwestern
Wisconsin
Minnesota
Iowa

South:
Ole Miss
LSU
Arkansas
Houston
Texas A&M
Texas
Baylor
TCU
SMU
Texas Tech

Midwest:
Iowa St
Missouri
Nebraska
Kansas
Kansas St
Oklahoma
Oklahoma St
Colorado
BYU
Utah

Pacific:
Washington
Washington St
Oregon
Oregon St
Cal
Stanford
USC
UCLA
Arizona
Arizona St


There'd be a few judgement calls on exactly how to break it up w/ some teams on the edges of the geographic regions, but that is largely how I would see it organized if the focus is 100% geographical.