I bumped into this spec and reading it, and I will come back later. Actually, I'm quite happy that things happen in the groups space. We need that. I'm not satisfied with either nip29 or nip72 or relays-as-groups concepts.
Do you have a working example application I can look at?
I am also thinkering on reforming nostr groups, and have drafted a spec, and some implementation, seen on
https://tribewiki.org/Tribe - feel free to steal anything from it!