Seems like a solution looking for a problem. Besides having the ability to create (or ban) an infinite number of accounts to rig a vote, instances have an incentive to keep the quality of content high.
If an admin wants to put something to a vote, they can, but even with a vote you can't force an admin to do what the community wants.
I think a lot of the potential problems this could solve can be better solved in other ways, i.e. account migrating to let people bail on an instance they don't like.