The bottom anchor has to be the evolution of goal-seeking "ought" qualia and the peculiar temporal persistence of "I am the kind of thing that makes more of the kind of thing I am". That's necessary to at least bring into sharp focus the self-contradiction inherent in any other view.

After that, yes, it seems to be the case that morality is a largely rational outcome given human nature, or rather, our intuitions are a good historical heuristic approximation (c.f. The Righteous Mind) which we can refine with cognition to be more consistent and work better in more diverse settings, just like we can with pretty much everything else.

I hope you write the article! I don't think there's actually all that much flexibility for different views; the only question is whether and where one stops paying attention to reality and starts inserting unjustfied assumptions instead. (E.g. Sam Harris with human flourishing--in some ways he's not far wrong, but he doesn't justify the underpinnings in a remotely supportable way, which allows him to retain a bizarrely individualistic outlook that I suppose is adopted from the culture he grew up in.)

Anyway, I'm curious to see how closely your thoughts on the matter align with mine.