I think your proposal of the detailed game might be interesting as well, but I am amused about your comment that the Gatekeeper is cheating when by default, he's the rules arbiter!
I definitely agree that the game lacks details. For instance, in an actual AI scenario GK-SCRIPT could assess positive utility! That's like saying "Oh, we can put a UFAI in a box as long as we make CEV the Gatekeeper, and have it destroy any UFAI that doesn't make itself a utility pump." Well, yes, I suppose you could, but I don't know if that's actually easier in the slightest,
Update 2013-09-05.
I have since played two more AI box experiments after this one, winning both.
Update 2013-12-30:
I have lost two more AI box experiments, and won two more. Current Record is 3 Wins, 3 Losses.