I accually, instead of messing with players, tried to do this with weapons.
To see what I could do, I imported the Old School Rifle into Shaper to find out Shaper is the most half-assed program out there.
The model imported with no problems. I looked through the animation list, and all of them were there. One animation was named "scope", I assumed it was a fail at creating an animation for using the scope. When I clicked it, shaper crashed. I tried modifying properties, etc. Still crashed. I think it had 0 keyframes, and I guess shaper is too badly made to handle it, so it just crashes. What I did after that is try to export it as a ASCII milkshape file, and shaper cannot do that because I get a lua error (because of scope animation probably). After that I tried the .x format, and I guess directX cannot handle exporting animations because when I loaded it into blender there were no animations (but a model still).
So, using this technique with items/weapons is literally the most painful stuff your going to go through in your life. The only way of customizing it reanimating the whole model.
Oh yeah, blender's directX importer cannot handle textures either, so good luck re-texturing the whole goddam thing.
EDIT: I tried this with the default gun, exported with milkshape ASCII and it looks super weird in blender, along with no animations. Same with directX.