The biggest thing missing from Mastodon remains the ability to *actually* migrate an account between servers.

The follower-migrate feature is not enough. I need to be able to migrate an entire account, including posts. And I should be able to do it without the former server cooperating (because of course servers can go down). I should be able to get some sort of cryptographic cert I can send to a new server with my posts and they'll be like "oh yeah, this is real, migrating u now".