1. I don't think the Pac12 would invite BYU under any circumstance. I don't think Utah would want it and I don't think BYU and it's baggage move the needle for any of the other schools.
2. I don't think the B1G would take any of the schools you mention. Why would they? If they wanted ISU or Kansas they would have invited them years ago, and those schools would have jumped at the chance, like Nebraska did.

Personally, I think what is more likely to happen is the Big 12 will sneak a couple of teams away from the Pac12. Arizona, ASU, Colorado, Utah seem like prime candidates. And if the Big 12 can get a couple to jump ship, then USC/UCLA could follow. Lording over the Big12 like Texas/OU has been a better position than lording over the Pac12, so SC might take the upgrade.

Whatever happens, it will be interesting..