MUH has a certain appeal, but its problems as well, as you say (and substituting CUH for MUH feels a little ad hoc to me), and I fear parsimony can lead us astray here in any case. I still think it’s a good attempt, but we should not be too eager to accept it.
Maybe you should make a map of reasons for why this question matters. It’s probably been regarded as an uninteresting question since it is difficult (if not impossible) the test empirically, and because of this humanity has overall not directed enough brainpower to solving it.
Wouldn’t that mean surviving alone?