Idea: multi-user tagging
If tagsistant will store permissions and ownership for tags and relations it can be used for "central file storage" of multiuser system.
Some tags and relations of other users can be included into relations by some users.
I.e., if any users supports its own collection of photo by tagging them, another users can refer to this photos from its own tag relations.
If I don't get this wrong, part of what you envision is already possible. Please mount Tagsistant with -o allow_other, then try to copy some content inside Tagsistant and later read it as another user.
But you're asking for user attribution of tags and relations too, something Tagsistant should store in its internal DB. This would allow a user to recognize not only its content but its ontology too from other's. I'll consider this feature as a future improvement. Thanks.