May be you're right. Try to include -pkg=<some-package-name> into the command line. <some-package-name> varies from game to game. Usually it is startup_int.upk, but Gears of War uses GearGame.xxx, Batman uses BmGame.upk etc. You should find package with common resources. I cannot do it for you because currently I have no Mass Effect on my PC.
Importing startup_int did not help, I have also tried importing other packages with a similar name, but ME2 has an ASSTON of packages, and it would take a very long time to go through all of them.
Also I think I know why certain meshes have purple discolorations: umodel cannot handle ME2 specular masks properly. I am pretty sure that it is the specular mask, because when I rotate the mesh in umodel the purple bands change, and only the meshes that use a specular mask have purple discolorations. Is there a chance you can fix this?