Remember, BYU's footprint isn't just Utah. It is the entire Western end of the US. We have tons of alumni in the three big Pacific coast states. They all bring eyeballs to any television deal the B1G may be dreaming up. And it is television revenue that drives the CFB engine these days.
Unfortunately, BYU has two strikes against it. It is not an AAU school, and it would be a geographic outlier (a problem we have with every P5 except the PAC12).
I suspect a football-only deal along with a scheduling agreement for basketball with some P5 would be the best for our school. That would juke the no-Sunday-play problem nicely, and give us the best of both worlds with basketball.
The WCC has proven to be a great conference for our non-football sports. We don't have to spend big bucks sending our non-revenue sports all over kingdom come every year, and it is super nice dealing with other private religious colleges. I would be loath to leave it for any conference other than the P12.