Group land locking?

while on the topic of the themed communities in the "Future SL Expansions" thread, i came up with this idea:

currently, land marked as no-build is no-build won't allow fellow community members to build on the land either. What I would like to see is a no-build-except-group option, where anyone in the group can build on land, but anyone who is not a member of the group, cannot. this way, community members can work together and collaborate on large projects, while simultaneously preventing outsiders from dropping random cubes or griefing items into the community.

Good idea.

If the land owner gives modify permission via the calling card to selected individuals, those individuals are able to build even though the land is set to No Build.