Let Parfit's mountain be a moral theory based on combining previous moral theories in a certain way. (Readers of the book referenced will be familiar with the form of this way. I read part of it, years ago, so I'll just use my "example" as an intuitive application of the 🗻.)
Is Moorean intuitionism (and the like) a rational enough theory to form a slope on the mountain? Suppose that we assert each slope's normative use to be a duty/right/good/virtue/value/w/e grounded in the very form of the theory of each slope. Then the Moorean interlude would be (if this is possible or sensible) something like a responsibility to develop ethical intuition---prior, then, to most or even all other applied intuitions?
This might seem a random, unmotivated image but consider that it is effectively equivalent to abstraction over the theological metaethics of the beatific vision. You can see this in Aquinas, but better in Dante, I think. From a moral point of view, one might say that C. S. Lewis's take on the Divine Commedy as science fiction in its own time is reflected in the theme in many sci-fi epics of cosmological knowledge gained in the endgame.
Is the question of deontic intuition fundamental, at least as a sort of responsibility unto itself, or even as the only innate "teleology" of ethical concepts?