Rules in my opinion would be: Permanent dungeons that can't be retaken. Saves us al the fuzz. Guild Leaders of each guilds are notified atleast a month forehand on that this process is in motion and get the opertunity to prove that they are "active". If they can't. Let's use the areas for something where everyone can participate and use the space!
As an old builder of the Toolset in nwn 2: I'll even gladely help in converting the "guild halls" into more..."rural/ruin like" areas with spawns scripts! ^^