Here is how I got MD3's to work, specifically one of a dragoon.
I had my good friend Raoni (co-partner on Dretch Range) eliminate all of the "states" of the dragoon md3 that I did not want/need (by states I mean different positions). He then exported it to me, and I put in radiant.
In radiant, I had to manually define the location of the md3 texture file using the _remap or remap key (I forget which one it is).
It's tedious, I know, but it works. Oh, and Raoni used Blender.