Why would most of the B12 and ACC be included? Only a few of the ACC are in the same type level and no schools in the B12 are at their level.
You're right that there is a clear separation between the P2 and the B12.
The ACC is currently tied with the B12, but the imminent post-GoR poaching will end that quickly. I've heard FSU and Clemson will likely end up in the SEC, where their fan bases and football-centric cultures fit in best, with UNC and Virginia going to the Big Ten. (Both of the latter are AAU members, which the Big Ten is emphasizing with any new additions.)
There's additional speculation the B12 could then swoop in to poach some combination of Va Tech, NC State, Syracuse, Ga Tech, and Louisville. (I'd frankly be surprised by Ga Tech. That program has fallen hard in recent years.)
The ACC would backfill with the 2PAC, plus high-end academic programs with good football and men's hoops. So add Oregon State, Washington State, UConn, Memphis, USF, and Tulane. They'd assumably cling to Notre Dame for OLY sports, but honestly, no one knows what the Irish will wind up doing when all is said and done.
As the dominoes fall, the American would need to replace three programs to get back to 14, or just one program to get back to 12. Unless there's pressure (and money) from ESPN to move to 14, I'd be surprised to see them go back to 14. So they'll likely only add a single team, either Georgia State or Texas State. My best guess would be the Panthers, who'd bring the ATL market (sorta), and marginally stronger sports overall. They'd pair well with UAB, who'd be losing their biggest in-conference rival in Memphis. And with Rice and North Texas already in the conference, Texas State would be an unnecessary redundancy.
At this point, the Sun Belt could attempt to poach a CUSA team (WKU? MTSU? Liberty? Kennesaw? JSU?) or could reach down to pull up a team from FCS (Mo State? Delaware? EKU? UTC?). All of these have baggage. WKU and MTSU have bad blood with the Belt. Liberty is still fighting the "Falwell" image and might overcrowd Virginia. Kennesaw is a direct market replacement for Ga State, and has great baseball, but has terrible football support and a history of bad D-I hoops. Jax State has never been a priority for the Belt. Mo State has lousy football support. Delaware just moved to CUSA and would have to pay GoR/exit fee penalties to make the move. EKU is EKU. And UTC doesn't have baseball, among other issues.
Mo State is probably the leading suspect, assuming they don't get grabbed by CUSA first, and end up caught in a GoR/exit fee situation which gets in the way. If that happens, they'll be in the same boat as Delaware. The reason I think Mo State would go over everyone else is that the Belt is leaning heavily eastward right now. Delaware or EKU (or even Liberty) would only make it lean even more precariously. The "central" teams like WKU, MTSU, KSU, and JSU would help balance things out, but only Mo State would really fix the problem.
Some might say there'd be a gaping hole in the ATL market if they don't add KSU. But there's two issues with that: 1) The SBC doesn't care about markets. They care about philosophical fits and fan bases, and KSU fails hard on the latter. And 2) Ga Southern probably garners more of the ATL market than Kennesaw. The SBC would still have a heavy presence in the state of Georgia, with or without the Owls.
Finally, CUSA would (at most) have a single hole to fill. Pretty much every team we could potentially lose has a decent replacement. Oh, it'd sting. No FCS team is as good as WKU, MTSU, or Liberty. And we wouldn't *necessarily* have to fill a vacancy right away. We're at 11 now. Ten is still a solid number, and it gives us each a bigger slice of the financial pie. And if -- by some stroke of *something* -- JSU ended up moving to the Belt, well, it's ultimately a lateral move, but it'd make a lot of Gamecock fans happy, making Southern Miss, USA, Ga Southern, App State, Coastal, and of course troy state into conference opponents. I don't see it happening. But it wouldn't be a BAD thing.
So back to the main point:
What do we all end up with?
For Football, the SEC and Big Ten are in a league of their own. No one else would come close. But the Big XII would still be head and shoulders above even the strongest G5s, and the revamped ACC would remain a notch or two above the American and MWC at their best. You'd almost have to concede them to the Power 4. But if they DID "drop" to the next tier, it would be a dream come true for the P2: they'd get to revamp the playoff structure in such a way that "lesser conferences" had a path to the playoff, and those "lesser conferences" could include the ACC and (arguably) Big XII. It'd absolutely shut the door on the current G5.
But when it comes to Men's Basketball, the Big XII would suddenly be a Power league, right up there with the P2 (and Big East). And the ACC wouldn't be too far behind, as long as UConn moved in and Duke remained. Essentially, in hoops, you'd have a Power 5 once again: SEC, Big Ten, Big XII, Big East, and ACC.
And those Power 5 teams could do whatever they wanted with the NCAA Tournament (and especially the lower tournaments, like the NIT).
So the G5 would be left to fend for itself, just as Derek Dooley recommends. I'm not sure I'm down with that idea. But it may be forced upon us.