The only way this makes sense is if the new teams add more than they take. This is a difficult proposition.
Here's the tool I'm using for this:
http://thequad.blogs.nytimes.com/20...-college-football-fans-and-realignment-chaos/ It's not perfect, but it's probably the best that we have.
The Big 12 fanbases rank:
#5 Texas
#19 Oklahoma
#29 West Virginia
#33 Texas Tech
#40 Kansas
#41 Oklahoma State
#52 Iowa State
#60 Kansas State
#65 TCU
#85 Baylor
Of course you can make the claim that these have changed over the last three years (this work was produced in 2011) - I would tend to agree in certain cases, especially with Baylor as they are probably higher than #85 today. But let's assume that it's all a wash, because again, we don't have better numbers.
The Big 12 average ranking of fanbase is 42.9. Meaning that any two schools that average out below that would be viable additions financially. Factor in the new money from a conference championship game that they would allow, and we could go to a slightly higher number than 42.9 and still come out ahead.
Now here are the potentially realistic options:
#43 BYU
#47 UConn
#53 USF
#55 UCF
#57 Boise State
#68 East Carolina
#70 Cincinnati
Any other school that you can think of (not already in a Power 5 conference or named Notre Dame) ranks higher than #70 and is essentially out of the running.
No school comes in "above average," although BYU is almost right on the average. UConn is close, and the Florida schools (plus Boise) are also somewhat close.
If the Big 12 was going to expand, I think a hard look would need to given to BYU, UConn, and UCF especially. I think UCF has more potential for growth than USF.
Of course, the Big 12 doesn't have to expand, and it isn't going to expand, so this is all a very moot point. I just prefer to look at these numbers when having our conversations instead of the people who just toss out a school like New Mexico because "it's growing." (New Mexico ranks #94 in fanbase.)