I've search the forum for this but the closet I've found is: http://empireminecraft.com/threads/sharing-sales-profit.52033/#post-935582 And this goes a bit hand-in-hand in stopping greifing in the frontier like PetuniaFigtree's idea of named blocks. I would like to suggest that Aproved Claim Owners be able to create a 'Claim Groups', add users to the group, and grant the permission(s) to other users of the group. Instead of being limited to your name and 2 others to an [Access] or [Locked] sign, the Owner (or one granted the perms from the owner) could create a [Locked] sign like: One sign that would grant access to everyone in the group. This could also be done for [Access] signs too so door access could be limited to the members of the group. Now everyone in the group can access that one locked DC.
I like that idea! I was out exploring and ran across a hidden base way out in the frontier; they had no doors! I thought that was pretty smart; blocks would have to be knocked out in order for anyone to snoop around in there - probably a great solution for a base with 2-3 members max but for us it's not feasible and the locked-doors idea would be perfect, especially if it could be applied to group.
