I think the best move for the B12 is to either convince a handful of teams from the Pac 12 to join to ensure their place in the top 3, or for the B1G to grab Oregon or one of the other top teams.
Either of those moves I think will destabilize the PAC enough to force the issue. If the B1G doesn't grab Oregon or Washington during the chaos, then we can add them to the Big 12.
After that the ACC is a dead man walking.
If something definitive comes out where Big 10 is not taking Oregon, that puts the PAC on life support and they could try to offer a good deal to attract some Big 12 teams, but I think those chances are small.
It looks likely that Oregon is heading to the Big 10. It seems like the most likely and probably lowest risk, reasonably nice reward for ISU is UW gets left out while Oregon bolts. That essentially kills the PAC while leaving a good brand in UW open to the Big 12. UW and Utah are the two 100% takes, no questions asked. They boost the media value of the league. Maybe not much, but some.
After that it’s more about getting enough good schools together to be too big to be left out of a playoff. It isn’t about optimizing media dollars per team anymore. It’s about doing what helps you maintain playoff access. Because if your league and school get relegated to a lesser division without playoff access the bottom drops out of your media value anyway.
Let the SEC and Big 10 blow up the ACC and take the top couple each and make $100 m per team at 18-20 teams each. Take the best of the rest. If that results in a 20-24 team league making $30m, so be it. And if an 8 team playoff with 3 auto bids for each of the three, with 5 at large that pretty much all go to the SEC and big 10, so be it. Just don’t lose access to the playoff.