Interesting, will check! For me the main problem of multisigs on nostr: they are needed for orgs, but they can’t serve orgs needs, since people in orgs are get fired and replaced, while the npub of the org must not change. This makes impossible any serious use case around multisigs in the current way they are set up (with Schnorr signatures and not in a GPG style).
Look nostr:npub13mhg7ksq9efna8ullmc5cufa53yuy06k73q4u7v425s8tgpdr5msk5mnym seems someone already took advantage of the fact nostr uses schnorr to make multisig publishing. I haven't used it yet to know the shortcommings, but seems to be the right approach for community owned nostr accounts https://github.com/nickfarrow/frostr . We only need to make better management tools and probably integrate it to some clients, but if it all works as I think it will, no new NIP's are required.
Discussion
Frostr does seem to address this. Good podcast describing it: https://stephanlivera.com/episode/476/