Nifty. Official WotC guidelines would probably insist on giving it an LA.. (OMG NATURAL ARMOR! LA LA LA!elevens)

The Monstrous Humanoid HD would be replaced by a class level for most characters, wouldn't it? Are the specifics of it just included for completeness?

The Ice caste's Natural Inclination appears a little odd. It would benefit Wilders, but assuming one goes with the favored (and mechanically superior) class of Psion, they'll be using Intelligence as the casting stat anyway. Seems like something of a wasted feature.
I was at least expecting someone to go, "WTF? A small creature with Powerful Build?"
Well, if you insist. Small Powerful Build?!? What's with that??