@jupiter_rowland @silverpill we are thinking of building a federated version of Facebook Groups, so people can leave Meta's cesspit.
What you describe sounds ideal - minus the science fiction at the end (we'd only need cloning/moving within our app initially).
And since it is new software then all the Mastodon problems you describe do not apply. All these features could be baked in from the start. We would need E2EE within the groups (so the host is blind) - just for an added challenge 😁