It is useless in that scenario, at least in terms of what we consider a conference today.
I've thought a lot about it, and keep coming back to the 48 number I walked through as a possibility a few pages ago, which ties into your main point. In a 48 scenario, not every team from the b1g/sec/b12/remnants of acc is going to get in. But most will. However, you have to remember to do the most important thing in this whole ordeal: follow the money.
Using current numbers, the sec and b1g combine for 34, leaving 14 openings. Here's where shit gets "fun" for us. FSU is doing their damnedest to bend over the ACC, and pretty much most competent people see the writing on the wall. The acc may not go the way of the PAC, but only because the majority of their membership will not have a landing spot in one of the sec/b1g/b12. Of course remember now, the new whatever league will still need some of those "bottom-feeder" teams to take the losses. However, it wouldn't surprise me to see a shakeup at that level. This is why the conferences of today must dissolve (or wither on the vine) to enter the new league. This would allow for the jettisoning of some less desirable teams in favor of more competitive, but still not a significant threat, teams that will pull more viewers.
This is how Rutgers, Maryland, Illinois, Houston, Cinci, etc get nixed. It's not that they get kicked out of their conference, per say, they just don't get invited to the new deal. However that shakes out, of course, but you get the idea of it. Kind of similar to how the SWC blew up to create the b12 from the b8 in the first place.
It still comes down to money, and how those paying the bill are best able to leverage their investment to generate as profitable of a return as possible. Illinois vs Rutgers, or IAST vs MissST? What's going to draw more between the two? Of course that's just an example, but those are the types of things that are being looked at for influence on how to get it done.
So back to 14 spots, and we'll say 4 teams total are not invited from the sec/b1g, so 18 spots. Those 18 spots will come from the acc, but mostly the b12. And of course, there will be a spot for ND, but only if they want it. I can't imagine they would still balk at the idea, but who knows with them.
The biggest take away for any b12 school, save a few, from this should still be to pump money into football. However, I do agree that also being home to many very good basketball programs will help. But there's got to be both, and football first on the list.
Right now it isn't about making the b1g or sec any longer. Now the play is through the acc, and either its transformation or destruction. Shake out the half dozen or so teams from that, landing in the b12, there you go. ACC no longer an influence, and now teams can be invited from the b12 and leave behind the rest.
If the b12 were at 22, and there were 14 spots available (maybe up to 18, but who knows), who would be the 8 not getting invited? Houston, Cinci, UCF, Baylor, of course. From there a hair trickier. Roaches? Tceh? Mormons? AZST? Ralphie?
Can't say SMU, because they wouldn't make it from acc to b12 in the first place. At this point, I'm guessing at most into the b12 would be all the desirable teams, that would eventually move to the new league: UNC, NCST, VA, VT, Clemson, FSU. Maybe swap in Duke, who knows. The execs have the numbers they can make money on, so they'll figure it out. However, one thing is becoming clear: How Rut/MD got into the b1g (cable footprint for b1g network) isn't going to fly in the new deal. It's going to be about how many eyeballs are brought and actually watch, not how many cable subs can have a few more bucks slammed onto them.