re: How to fix the Big 12

I'm not sure you can really. The more desirable schools you might like to add from the ACC are bound by their own GOR. The Big 10 and SEC schools do better financially remaining in the conference where they are. That means grabbing up another couple midmajors if they are to expand. The options would seem to be:

New Mexico - only 2 million people in state, not great, not a national or great athletic program
BYU - religious affiliation is less of an issue for a conference with Baylor, only 2.9 million people in Utah. a better athletic program than the likes of New Mexico tho
SDSU or another Cali school - distance is an issue but the idea of reaching into California should be given more consideration. Imagine the games between WVU and SDSU tho :/ That's a road trip
Memphis - more regionally logical. Great basketball program. Not a terrible football program. Should be considered (Tenn has 6.4 million people
Cincinnati - great basketball program. Big state to add with 11 million people. This should make them a favorite IMO over options like New Mexico and BYU