Maybe you could use the files from the SWBF1 mod tools?

Quote from: Isaac1138 on November 07, 2023, 08:24:36 PMYou would duplicate the mesh and prefix "sv_***"

More info here
https://github.com/PrismaticFlower/SWBF-msh-Blender-IO/blob/master/docs/reference_manual.md

The mesh becomes collision. Is there a way to avoid having the 'shadowvolume' become collision?

Import one of the existing models from the modkit. look at the naming of the bones, then add a skeleton to the mesh. Next step is to add more bones to the skeleton. Since the model isn't t-posing, you will have to replicate the characters pose with the bones.

Lastly, ensure your skeleton has the same amount of bones as the official clone trooper/stormtrooper. When that is done, you select the skeleton, switch to pose mode, select your 501st stormtrooper mesh in the outliner, press CTRL + P, select automatic weight in the menu that shows up. Now your model is rigged. Your model might not be perfectly rigged, but at least you can try it out in the game. You can also improve the rig by repainting the weights of your rigged mesh with the wight paint mode and or using assign on the newly created vertex groups.

I know this is an old post, but do tell if you still have use of it, I will sleep happy knowing that I have been of use.