IMO, adding Louisville is a no-brainer. The old Drake-Louisville rivalry was an epic one in the old MVC days with Drake and Maury John. So the logistics makes sense. Besides the fact they have a good athletic budget and athletic department.
WVU is also a no-brainer. But they will end up in the SEC most likely if Mizzou stays. Prefer Mizzou to stay. And even if they do then you pursue WVU. But most likely you will get one of the two.
Next up is TCU. Logistics and available. Another Texas team, I know. But still. We lose aTm and offset that with a decent TCU team looking for a BCS home. You pluck them before they truly enter the Big East and Louisville has even more incentive to come to the Big 12. So
2 reasons for picking up TCU.
Last up would be Cincinatti or BYU. BYU has been argued for. And would be an okay get IMO. Cincinnati has potential with a lot of TV sets but is in a Pro Sports town. Cincinnati is already a BCS school. BYU has a decent fan base but logistically is a little out there. But in this day and age, not as big of a deal.
So my prediction is:
TCU comes on board right away. And we go with 10 teams.
Mizzou stays then WVU goes to SEC.
Mizzou leaves for SEC then we will add BYU right away and WVU will be available after the waiting period.
BYU will be added but they may remain independent until Louisville joins. The timing of their joining completely depends on whether Mizzou stays.
Louisville will be added after the waiting period.
Big East will try to poach the teams it needs from C-USA to remain as a football conference. But with UConn and Rutgers slated to eventually go to the ACC, it is doubtful they will survive. They will become a BB only conference. And Cinci will slide back to C-USA as the Big East ceases to exist as a football conference.