If you'd go to that level of collusion, you could just fake logs. At the point where both sides are in on it, there's basically nothing that they could say that would be convincing.
I think some of the latter, non-Eliezer games used a third-party observer. It's definitely a good idea, but I don't think Eliezer wants to repeat his games. Not a good state of mind, as he said, and I'm willing to believe it due to corroborating experience with other players.