Im planning to investigate this by looking at the dark templar models seeing as there are 2 different ones. But my first step is to try and get skin changes working from a seperate file rather than editing the base.mpq. That way you can swap files in and out of the directory to play with a different colour set or something.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.