If I'm correctly understanding what you're claiming, it's something like this: "One can postulate a supremely good being without needing human-level concepts that turn out to be really high-complexity, by defining 'good' in very general game-theoretic terms". (And, I assume from the context in which you're making the claims: "... And this salvages the project, mentioned above by CCC, of postulating God as an explanation for the world we see, the idea being that ultimately the details of physical law follow from God's commitment to making the best possible world or something of the kind".)

I'm very pessimistic about the prospects for defining "good" in abstract game-theoretic terms with enough precision to carry out any project like this. You'd need your definition to pick out what parts of the world are to count as agents that can be involved in game-like interactions, and to identify what their preferences are, and to identify what counts as a move in each game, and so forth. That seems really difficult (and high-complexity) to me, whether you focus on identifying human agents or whether you try to do something much more general. Evidently you think otherwise. Could you explain why?

(I'll mention two specific difficulties I anticipate if you're aiming for simplicity through generality. First: how do you avoid identifying everything as an agent and everything that happens as an action? Second: if the notion of goodness that emerges from this is to resemble ours enough for the word "good" actually to be appropriate, it will have to give different weight to different agents's interests -- humans should matter more than ducks, etc. How will it do that?)