@Gargron on a random note this reminded me of an idea I had.
I was thinking of how you could create a portable federated profile, and it could work similarly to SSH keys.
You could generate a key pair on the home server, and use the private key to encrypt your profile info.
Then when you create an account on another server, paste your public key, and it will try to pull profile info from your home server and try to decrypt it using the key your provided.