Yup totally with you, being able to choose the notes you can and can't see through their domain affiliation is awesome.
Whitelist + blacklist for clients maybe, filter by nip05, not just WoT or relay choice but implicit rules like a firewall... small communities would love this so they can exist in their own pocket of the internet without spam or intervention from unknowns.
Surely this could be a model for more usage of nostr without nostr even being known to be the underlying tech?