The last time the Big 12 looked at expansion (for example), Memphis (and FedEx) basically offered to take none of the revenue from the conference for something like 8-10 years, whereas BYU pushed for an equal split as soon as possible. BYU definitely brings a lot to the table, but there's enough about the finances that I don't think any of us can say we know the best financial choice. I do think UCF has the most opportunity to grow though.
That's why I'd probably go (from Big 12 perspective where W Virginia weighs heavily)
1. UCF
2. Cincy
3. Houston
4. BYU
5. Memphis
And then a bunch of also-rans. It's the same reason BYU hasn't been invited to the top G5 conference (AAC). BYU would be a nice addition, but to have BYU make sense would require adding several others as well.