When you have NPC's that are taking your loot, just fill up their slots with items (such as potions and boots and gloves) and they wont be able to take the magic weapons etc that you get during the game (as they wont have any free spots available).
Also, once they have a huge pile of YOUR GOLD in their inventory, just stand outside the church, move the NPC away from your guys and use fireballs near him/her until their dead. Transfer all their gold to your inventory, then simply go inside the church and ressurect them (cost 750-1000 gp to ressurect, so make sure they have enough "loot" of yours to make it worthwhile. I have "killed" and "ressurected" Otis (10th level NPC) fighter about 6 times so far. I even did it to the King of the Trolls for kicks and i am now wearing his troll armor, and helmet and he doesnt seem to mind. Just be careful, Otis doesnt like it if you mess with his "otis longsword or chainmail", everything else seems to be fair game. I even got the Rogue's ring of invisiblity that way from the tavern after he joined me.