Nice, I think I followed this post (though how this fits in with questions that matter is mainly only clear to me from earlier discussions).
We then get those two neat conditions for cooperation:
Significant credence in decision-entanglement
Significant credence in superrationality
I think something can’t be both neat and so vague as to use a word like ‘significant’.
In the EDT section of Perfect-copy PD, you replace some p’s with q’s and vice versa, but not all, is there a principled reason for this? Maybe it is just a mistake and it should be U_Alice(p)=4p-pp-p+1=1+3p-p^2 and U_Bob(q) = 4q-qq-q+1 = 1+3q-q^2.
I am unconvinced of the utility of the concept of compatible decision theories. In my mind I am just thinking of it as ‘entanglement can only happen if both players use decisions that allow for superrationality’. I am worried your framing would imply that two CDT players are entangled, when I think they are not, they just happen to both always defect.
Also, if decision-entanglement is an objective feature of the world, then I would think it shouldn’t depend on what decision theory I personally hold. I could be CDTer who happens to have a perfect copy and so be decision-entangeled, while still refusing to believe in superrationality.
Sorry I don’t have any helpful high-level comments, I think I don’t understand the general thrust of the research agenda well enough to know what next directions are useful.
You are probably already familiar with this, but re option 3, the Multilateral AGI Consortium (MAGIC) proposal is I assume along the lines of what you are thinking.