BYU going back to the MWC is not a given, even if that is what BYU wants to do.  They burned a lot of bridges when they left.  I am not sure that Air Force, Colorado State, New Mexico and San Diego State would vote to allow BYU back in.  I'm not even sure Utah State will not see this as a chance at some retribution for not letting them in the WAC all those years ago.  I don't know if Hawaii has a vote.

Yes, BYU brings a lot of advantages to the MWC, but is that enough to overcome hard feelings?  I think it is wrong to assume that BYU can just go back if they want to.