Someone (I forget who) used just such a pretender in the Faerun PBEM game. It was very successful (holding off Mictlan and Ulm), until it got magic duelled and their war effort collapsed.
Thats just the thing, you're using all those points on a single unit that can be (with good chances too) killed off by a Astral 1 spell. Works great until that happens though.
Hes already ethereal and Shinuama have access to same astral magic(lucky pendants/antimagic amulets) dont they? He already has plenty of buffing to do so why not just drop the astral magic(and maybe 1 level of dominion, 10 seems a little much on a ghost king) and buy some more scales?