That would absolutely work, 10th. Because of regional pride and simple geography, I totally understand why the Texas schools would want to stay together. With understanding that Houston and SMU would take a call-up, a conference of the following would be intriguing. Texas is like its own country... there would be no lack of financial or fan support for such a conference. No particular order:

1) Houston
2) SMU
3) Rice
4) Tulsa
5) Tulane
6) Texas State
7) UTSA
8) North Texas
9) UTEP

With that as a core, I would think that New Mexico State would make sense at 10, but they could add La. Tech or La. Lafayette if they wished to go along with Tulane. Whichever of those LA schools did not go to Texas would be perfect for that Southern Conference. You may be right about Texas State, though... one of those TX schools may prefer to break out from the mold and establish a more southeastern identity, similar to TAMU. I don't have a good pulse on it. I do know that MTSU has great relations with North Texas. I think North Texas or Texas State would be great.