I've searched all over but there seems to be no way to create a single player versus A.I. game (i.e. one that would allow cheat codes) with arbitrary team sizes, e.g. 1 versus 7 or 2 vs 6 on an 8-player map.
In Starcraft 1, I enjoyed playing against many AIs with cheat codes enabled to give me a chance. In Starcraft 2, the UI acts as though I'm allowed to drag team members arbitrarily, but in an uncharacteristically poor UI design by Blizzard, simply fails to add them without any indication that I did anything wrong. I've tried changing the game mode to custom game, custom teams, etc. And it still doesn't work. Any clue?