The Big12 rights value would decrease considerably and the Big12 would scramble to stay a lesser P5.
UConn was the obvious Big East target getting the conference to 11 members. The only other target that would make sense for going to 12 members and a bloated 22 game conference schedule is Kansas. Adding Kansas on the western door with Creighton would be a coup for the conference and for FOX, assuming we extend with our TV partner. The Big East would have 3 legit Blue Blood programs - Kansas, UConn, and Nova.
If Texas and OK move it would be the time to appeal to Kansas to make a basketball-first move. Fox would need to provide the incentive for the move - a Notre Dame / NBC type Indy football TV deal in addition to the Big East contract. Fox would be overpaying for the football, but cherry picking Kansas without over paying for other programs in a watered down football conference. In this arrangement the Big East programs might not see the full increased value of Kansas, as some of that would be baked into their football TV deal, but maintaining and extending our current Big East TV deal would be good enough. We'll take a $5M per year per team deal plus the added benefits of Kansas on the schedule and in the conference.
The Big12 then moves to recover and actually goes to 12 members raiding the AAC: Baylor, Iowa State, Kansas State, OK State, TCU, Texas Tech, and WVU add UCF, USF, Houston, Cincinnati, and Memphis. The Big12 adds the coveted Florida footprint and brings in Cincy and Memphis as more regional foes for WVU. The Big12 maintains P5 status with these adds but likely loses broadcast rights value.
