See this post: https://rustedneuron.com/web/statuses/105748123175852813
I think Federated Identities is the missing piece. I should be able to participate in every aspect of the social cloud, while using only one identity for all of them.
(Unless I have some reason to create other identities. Although a dark pattern there is 'Sock Puppets'.)
This makes it simple and it means a video I post on PeerTube can be cross referenced to my Mastodon toots and Lemmy posts, everything linking back to the one identity.