Essentially, what you're describing is just the situation that we are actually faced with.

I'm glad it all adds up to normality, given the amount of ink I spilled getting to this point.

And you're saying that you don't expect this situation to change significantly by the time we build an FAI, so the best we can do is equivalent to a group of uploads improving themselves to the best of their abilities.

Not necessarily. The uploads construct could in principle be made abstract, with efficient algorithms figuring out the result of the process much quickly than if it's actually simulated. More specific heuristics could be figured out that make use of computational resources to make better progress, maybe on early stages by the uploads construct.

it doesn't really constitute a meta-ethics, at least not in the sense that Eliezer and philosophers use that word.

I'm not sure about that. If it's indeed all we can say about morality right now, then that's what we have to say, even if it doesn't belong to the expected literary genre. It's too easy to invent fake explanations, and absence of conclusions invites that, where a negative conclusion could focus the effort elsewhere.

(Also, I don't remember particular points on which my current view disagrees with Eliezer's sequence, although I'd need to re-read it to have a better idea, which I really should, since I only read it as it was posted, when my understanding of the area was zilch.)