Discussing the solution would be to accept the premise. And the premise I think is flawed, pun intended, so let’s adress it first.

Majority of instances are extremely small, so if you are correct on the surface analysis that most fail, it may simply be people giving up on their venture for going to a place more stable and that they don’t have to manage themselves.

Also surface analysis is another problem by itself because the premises for it can be faulty, and saying as if it’s a certainty can help spread misconceptions. And there’s also the problem of the sensationalistic tone.

And on communities failing, define failing, please. Some may indeed, but what if they simply represent a topic so niche it rarely warrants discussions?

And on migrating, if the very top is problematic, voting out can be hard too. Even more so if it’s the guy paying the bills or managing the infraestructure. And also example comes from the above, as the saying goes, so users cather to the culture they want to see fostered by the administration.

Furthermore, still on voting, who’s to say, if voting is implemented, bot and paid actor accounts aren’t made discretely over time to rig them?

Also, what works to one group may not work to another, or even to the same group in different periods.

And still on migrating overall, since here’s a network, not simply just a bunch of social medias aware of one another, if you make an account on a new platform, there’s a kickstart of potential users since they’re still in the network.

And regarding the network aspect, using a software with microblogging integration such as Mbin, Piefed, Catodon or Friendica can give an even further push, since then you can use hashtags, boosts, following besides subscribing, community packs, etc.

Also on being a network, you can use relays, such as Threadirator and the other project with a same purpose I always forget the name. That helps making it appear on the connected instances.

And with the problems I could notice out of the way, no onto the proposed solution alternative:

The fediverse is a network, so you are free to make an instance to try that yourself. Or also to approach instance administrators to see if they’d be willing to experiment, since people can be rather approachable if you ask them directly.

And if the idea works out, similar to how historically it goes, people will copy the model. But a beautiful idea on paper means nothing without concrete examples. And as it’s presented, it sounds more like a liability than a proper model.