So on fediverse at the moment I guess we have multiple identities, multiple services + data stores.

One step could be one consolidated identity using multiple services and data stores.

Personally I like the sound of a generic AP server + data store, e.g. CommonsPub, to which other services authenticate as clients, and all my data is in one place.

You could host your own data store, or still have it live on a shared instance. It would be simple to migrate it elsewhere if instance goes kaput.