This is an interesting point, I think. What you have with descriptive, normative and metaethics is a gradual process of stepping back: we describe what is moral within a given moral system; that system itself justifies moral actions by appeal to some feature (correspondence with an ideal, moral law, utilitarian calculation, etc.), and then metaethics analyses these various moral approaches.
To step back from this again would be to generate a sort of meta-metaethics, which looked at the need to classify moral theories, perhaps (or using some other criterion which allowed us to step back). This is possible, but it is something that gets more abstract and difficult and perhaps more general (so, more about philosophy and less about ethics itself). Also, I don't think this could keep happening (e.g. meta-meta-metaethics) without getting pointlessly confusing - and disappearing somewhere where the sun don't shine!
Having said that, there are various approaches which try to step back in this way. Nietzsche does it to a certain extent, and in a sense his whole philosophy can be seen as a stepping back from traditional philosophical concerns in order to ask subtler questions. Also, this seems to be a theme running through post-modern continental philosophy - e.g. Foucault, Derrida, etc. In fact, from my understanding (which is admittedly little in this regard) Deconstruction seems to involve nothing but stepping back and reinterpreting traditional questions in a new light.
However, as I've said, there is a limit to this, and whilst it can be very illuminating when you have something interesting to say, it is pointless to do it just because you can. Also, however, there would appear to be logical limits. For instance, if I want to step back and show how some theory or philosopher - or even a whole philosophical tradition - is driven by some prejudice, or some view of the world, then what is there to stop someone accusing me of the same type of thing? This is a constant problem for such things as Deconstruction, and is a common criticism of Nietzsche himself.
Sorry for the length of the post - hope this helps!