UCF is easily the best choice on the board, especially thinking longer-term. That said, BYU wouldn't be an insane choice and I think they'd have a real shot if W Virginia wasn't in the Big 12. That really hurts BYU imo.
Also, if BYU did get into a P5, I fully believe they could move above the Oregon State's of the world. The unique factors of BYU help them stand out now, but would (for football purposes) largely make them stand out in a slightly negative way if they were P5, but I don't think it would be a huge impact.