Well, with the guards, they could just stay put at the gates. Therefore, the only time they could lag anything is when an unfriendly comes into their "vicinity." Then they would, obviously, attack whatever comes near. They could then loot the corpse as well. I would think that a fairly simple script could do that (although I am not extremely knowledgeable on scripting).
I know that other servers I have been on have the guards... although I do not believe they did any looting.
So, no movement needed unless an unfriendly character arrives. I doubt that the guards just existing could really put that much of a damper on the server. But, then again, I don't know much of the programming behind NWN either.