That will only allow you to attack other players with the pvp flag on.
There is no command to actually take over and control an npc. You need to make a new character, #name it what you want it called, #permarace it to the race you want, #level it, etc. Turn your gm flag on (#gm on), then use /becomenpc <npcrace>
In my experience that tacks an annoying "Trader" title to your name, though. So, you'll become "Trader Mummy Leader". If you don't like that, you can avoid using /becomenpc, and just make a #damage hotkey to use instead of attacks. But, it wouldn't really be fair, because the players can't attack back. They CAN attack you if you use the /becomenpc command. In short, there's no good way to do what you're trying to do, but I'm with you 100% that we need a better solution.
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