"create an AI that minimizes the expected amount of astronomical waste"

Of course, this is still just a proxy measure... say that we're "in a simulation", or that there are already superintelligences in our environment who won't let us eat the stars, or something like that—we still want to get as good a bargaining position as we possibly can, or to coordinate with the watchers as well as we possibly can, or in a more fundamental sense we want to not waste any of our potential, which I think is the real driving intuition here. (Further clarifying and expanding on that intuition might be very valuable, both for polemical reasons and for organizing some thoughts on AI strategy.) I cynically suspect that the stars aren't out there for us to eat, but that we can still gain a lot of leverage over the acausal fanfic-writing commun... er, superintelligence-centered economy/ecology, and so, optimizing the hell out of the AGI that might become an important bargaining piece and/or plot point is still the most important thing for humans to do.

Metaphilosophical AI

The thing I've seen that looks closest to white-box metaphilosophical AI in the existing literature is Eliezer's causal validity semantics, or more precisely the set of intuitions Eliezer was drawing on to come up with the idea of causal validity semantics. I would recommend reading the section Story of a Blob and the sections on causal validity semantics in Creating Friendly AI. Note that philosophical intuitions are a fuzzily bordered subset of justification-bearing (i.e. both moral/values-like and epistemic) causes that are theoretically formally identifiable and are traditionally thought of as having a coherent, lawful structure.