This proposal to separate your ActivityPub identity from the server on which you reside is promising (and addresses my biggest gripe with AP), though I'm naive to the process. How far could it be from making it into the standard, and what sort of migration pains would implementations like Mastodon face?
https://codeberg.org/fediverse/fep/src/branch/main/fep/ef61/fep-ef61.md