Much like the PAC-12 and California, the Texas teams have to be split between the two divisions. It was one of the things that split the original Big 12 up, the North schools want the games in Texas for recruiting (though it also hurt that they split Oklahoma and Nebraska).

I think you likely do something like BYU/BSU/CSU/KSU/Kansas/Texas/TTech in the west -- though you then also need one permanent cross over to allow Oklahoma and Texas to play annually (or replace the Kansas schools with the Oklahoma schools).