I agree it's unlikely. It's just what I think would be the best way forward. At least each state would be equally represented in the governing body so maybe that could help with consensus-building. In my dream world, some of the SEC states like Texas, Alabama, and Florida come together for it and then start politicking smaller states like Missouri and Arkansas into joining.
I have no idea about existing entities. The NCAA and conferences will only ever be able to govern around player eligibility and school participation (e.g., bowl bans, scholarships) in NCAA or conference events. And I have no idea where their authority actually falls for NIL.
I don't think the end goal should be to replace the NCAA. It could happen with a conglomerate of the conferences, CFP, and March Madness (if the last two are even separate from the NCAA) but then there would still need to be other organizations that step up to handle the national championships for other sports. And it would also mean the conferences would start having to do a lot of stuff they don't currently. At least based on my understanding of how all these organizations operate.