The idea that Ole Miss and Vandy, founding members of the SEC would be kicked out of the SEC is absurd. There is no one saying this right now. No one is even thinking about it. I'll concede that if they ever just go to new leagues - Nike and Amazon - that teams like Vandy would be left out. But that scenario is even more absurd. It's like you aren't even thinking about what makes CFB special and valuable. Sure, we know it's about money, but your scenario and those who keep bringing this up aren't even giving a single thought that no one would like what you suggest. Sure, there is a ton of change, but none of it has changed to the foundation of what CFB is - student athletes - yes, a huge percentage of the players are still student-athletes and want to go to the school of their choice, fans that are fans because they attended the school, tradition (yes, it still exists, even with teams moving), bands, cheerleaders, etc. If that goes away, so do most of the fans, including me.
No, the mid schools will not want to become the bottom schools. That's obvious. So they won't vote for the mess you are laying out. It's why the SEC won't add FSU and Clemson ... more schools don't want to make it harder to get into the CFP, go to a bowl game, or possibly win the league. Hell, why would UTjr want to bring in FSU and Clemson, two losses for you? You haven't sniffed a NC or an SEC championship in almost 30 years (not being an asshole, just pointing out that while you are talking about Vandy and the Mississippi schools, the top teams think the same thing about your team these days). Why would you want to bring in two schools better than yours making that harder? You wouldn't and your school won't vote for that. We saw this first hand last year when the mid and lower schools in the SEC said hell no to going to a 9th SEC game.
You are totally wrong about the NFL. It's designed to drive parity. The draft, scheduling, salary cap, revenue sharing, are all designed to drive parity so that the worst teams can have a chance to get decent and maybe win. Sure, the better teams will win more, but look at New England these days, Dallas, etc. That level of parity doesn't and can't exist in CFB. You can't force players to go to a school they don't want to go to, the scheduling is all over the place and with 134 teams v. 32 you can't schedule parity, and certain teams will always have geographical, financial, and other advantages that can't be smoothed out. So, no, IMO CFB isn't ever going to be like the NFL due to built-in inherent aspects of it that can't or won't be changed.