I mean, I have a knife. It should take a sidearm slot but it won't work, as sidearms don't have stroke anims. It works as a primary weapon but who would want a knife to replace M16?
If it's a dummy weapon it will work, but with no model.
So if the anims could be changed (Can they?) it would probably work.
And what the hell is "Cannot open object data3d"?!?