Air Force? That would be a financial disaster for the conference. They would bring no revenue to the Big 12, and just diminish ISU's slice of the pie even more. It would be even worse than adding a MAC team.
I may be wrong, but I disagree that it would be a "financial disaster" for the conference. I'm honestly speculating, but I would guess if you put AFA in the Big 12 they would be picked up on the Armed Forces Network worldwide for nearly every game. I'm not sure, but I would guess that AFN would have to pay the conference to broadcast those games. Add to that the fact that you have a ton of Air Force personnel around the country that would watch, and just Americans in general who pull for the academies and you have a large fanbase. Just look at how many Army fans showed up at ISU for the game last year. The american public loves seeing the academies do well. I know I cheer for the academies to win unless they are playing my team.
You can disagree with my logic, and if so I would be wrong. I may even be wrong about AFN paying for broadcast rights. But if I'm right there is no way that adding a service acadamy would be "financial ruin" for the conference. I just don't see adding a school which represents a branch of the United States military made up of 330,000 people (active duty) as a bad move financially. That doesn't even include retried personnel, reserves, or civilian personnel. If you put them in one of the best athletic conferences in the nation you will get a very solid following.
But that's just my opinion. I mean considering ISU only has 215,000ish living alumni (many of which don't care at all about athletics), I would think a group of 360,000 made up of 80% men with an average age of under 35 may provide the conference with a good amount of marketability.