Fedgar, I understand your concerns, but the key to a successful factionbase is walls of obsidian, lava moats, and water on the outsides of the obsidian wall. Those elements make the wall nearly impossible to break. and perhaps we can make a message that pops up in world changes stating "This world does NOT permit grief." and "This world is the Raidlands, there is HEAVY PvP and grief."
Just some idea's to that.