So, I finally got around to reading up on some of the tools so I could try to make this work. I realized that I'd also need to make a new material instance, though, since the file includes a material and texture, as well. I made a new ArmorAddon entry to separate out the raider and gunner instances and make the raider instance reference the new nif, changed the references in the model nif ("Raider04FShort.nift") to reference a renamed material file ("Raider04FShort.bgsm"), and changed the material file to reference the texture that I also renamed ("Raider04FShort_d.dds", I believe). What I see in game is the model, but with the material not showing properly. The actual harness mesh is purple. It shows up fine in nifskope, and if I turn the material into a material swap in the CK, it shows up fine on the normal harness mesh, so I feel like I must have missed a reference in the mesh file. I don't know where it could be missing, though, since I thought I replace all the entries. I'll look at this again the next time I have time, but figured I'd see if anyone might have some idea of a detail I might've overlooked when setting everything up.