If you want to add to the XII you have to look at major institutions in traditional football areas. Forget the BYU's of the world, not enough people and TVs. There are no major schools left west of us worth pursuing. Forget Texas, too much demand there already. Look to the SE and look for any state school that is not already taken. I present two.
The University of Central Florida is an American public research university in Orlando, Florida. It is the largest university in the United States by undergraduate enrollment. They just hired Scott Frost, former Duck OC, as their coach and appear to be committed to football.
Georgia Southern University is a public research university located on a 900-acre (3.6 km2) campus in Statesboro, Georgia, United States.[3] Founded in 1906, it is part of the University System of Georgia and is the largest center of higher education in the southern half of Georgia.
These would provide natural rivals to WV, location wise.
I would submit that the XII go after these schools, take TV money and help them build larger stadiums.