The problem with What if's is that you are adding a lot of guessing. I really believe that the BIGXII was a 1 team or none conference. No way Baylor or TCU was getting in... and by crowing a co-champion, that messed up everything for the BIGXII.
OU and Texas are the only 2 teams that could make the playoff together. The SEC could easily have up to 2 teams in the hunt every year. The BIG10 is the closest to having 2 teams in the playoffs... the PAC is a virtual lock every year with 1 unless something bad happens the last couple of weeks of the season.
The BIGXII will always be in a dog fight with the ACC and SEC 2nd team and maybe a BIG10 second team every year because of there lack of a conference championship game and being a relatively weak conference.