Tested them and they look very good so far

However I think they should be a bit bigger, when a player explodes in them it looks like half of the body vanishes in the air. Maybe some bent metal patches would look nice as well, not only mechanical parts.
Couldn't help it and made two screenshots of how they look like as gibs (just replaced the original gib models with them, no per player gib code yet).
I'm tempted to try making the alien ones myself, though I still have some problems with specifying the textures and shaders correctly in Blender so in the worst case I'll just pack them as .blend files.