I think that Rumple is not so much power hungry as he is using power to “protect” what belongs to him. In Desperate souls he says something that he was not afraid and that he protected what belongs to him.
Ofcourse, “protecting” your loved one doesn’t mean you need to kill the mute maid…so its an abuse of power Rumple’s dealing with…not that he wants to take over the entire world or anything. What the writers have made clear is that Rumple/Mr. Gold has a very specific code he’s following…and I think that’s using the power to find Bae.
I mean, if you were a really power-hungry person you would 1.Take over a kingdom., 2. Have the entire FTL bow down to your feet, and 3. Get all the gold and riches for yourself.
Ofcourse, once Rumple achieves his goal of finding and protecting those he loves…we will see what his motive might be then.