I'm not very sure what the OP has against Astral and Umbral elements? I mean, it's not like our elemental relationship is centered around the Astral/Umbral relationship, unless I misunderstand things.

Astral and Umbral are like our seventh and eighth elements, though they're combinations of elements. I think it's a pretty interesting and unique concept, and i'd sincerely like to see it worked on a bit more and used a little bit more often.