Slightly similar to this
On a server, only admins can place zones called "Build" or "Anti-Build" zones. There is an RTB pref that determines whether or not other players can build outside of zones. If the option is ticked, all non-admins will not be able to build anything outside of zones. The only place they can build is inside a "Build" zone. If the option is not checked, non-admins can build wherever they like, excepting "Anti-Build" zones.
Basically it's like the v0002 Blockland where there were pre-determined spots to build.
I love the zone idea though the OP presents, and for what kind of server and stuff it could be used for.
