The ACC must have ND and USC.
Then offer the B1G any or all of the remaining AAU schools.
The ACC would then promise to have a home for the rest. Non AAU schools Arizona State, Oregon State, Wazzu. We also will take Stanford (for ND) with promise that the Cal-Stanford and USC-UCLA, ASU-UA, UO-OSU, UW-Wazzu games will be preserved in OOC.

That would put the ACC at 20 and the B1G at 21 (with ACC getting Stanford); or 19 and 22 with Stanford staying Pac12-B1G. The ACC could add some BigXII members too (ND loves a Texas opponent?). And who knows, if the map disappears on the SEC, they might even take a few teams that they hadn't planned on: WVU? Kansas?

This would solve many problems.
-Pac teams need Eastern exposure. This will give it to them. Saves all members.
-ACC needs to survive. This may do it.
-This clears the brush for the BigXII leftovers and gives them the chance at a P3 conference or at least shows them the certainty and clarity of the scene.
-I do think the SEC wants to keep a regional flavor. But the ACC and B1G should be trying to go transcontinental.
-ND stays away from B1G and has far more control over its own affairs.