first of all, BYU is only going to join another conference (other than the Pac-12 or Big 10) other than for football only. they won't move all sports to another conference.

2) the Big West is like the WCC. the difference is they have Gonzaga and BYU, and we have Hawaii as our BYU. My worst fear for the Big West is if the WCC tries to bring over Hawaii, and lose whatever regional luster the Big West has left

3) the Mountain West is the most stable of the non power 5 conferences, the plus for the MW is they have some decent teams to be considered, the negative is they are stuck as the next best thing to a power conference; and they just can't make themselves into a power conference. They would take a huge risk to take on more eastern teams that frankly wouldn't add anything other than more teams. They have one thing going in that in each city they are in is the 'game in town' (aside from San Jose),for college sports, they shouldn't forget that. Yes Fresno, San Diego, Las Vegas, Reno, Boise, Albequrque, Colo Springs, San Jose, Hawaii aren't media drivers, but they've got a unique footproot in some sizable cities.