I would like to build something in that direction, but I see too many unsolved questions to just start bootstrapping. Your notes definitely inspired me to do more research on map data formats, editing and rendering today.
Discussion
Instead of just maps we should have a Nostr based cadastre.
And instead of only Nostr, it should tie into a universal identity system like what #[3] works on with https://pkarr.nuh.dev .
pkarr is awesome! Thank you for sharing