1. Adopt some DID method for actor resolution (to make it easy to port identities around)

2. Add a "strict mode" where documents are only accepted if properly signed (so that servers no longer are the authoritative source)

3. Leverage content-addressable systems (IPFS, torrents + magnet links) to serve media and documents (so that even if one server goes down, the data can be fetched in the Fediverse itself)

That's it, really. The main problem is social: item (2) would bring non-repudiation (anything you write would be undeniably yours) and most people would be concerned about participating in a social network where anything you publish is recorded forever.