Why are the Pac 12 and Mountain West dancing around the obvious that they need each other?
Unless the Pac 12 teams which bounced to the Big Ten, Big 12, and ACC return in the fold... or if you add someone like BYU... you basically have two incomplete, underwhelming conferences.
Together, you have something. Probably the worst Power 5, but still, something.
By themselves, you are just teetering.
Combine the best 12-14 schools, and then try and add back the schools which left.
Start with the ACC schools as they should be the easiest to add.