Hi, so I went through the steps above, but I kept getting this when I started up the game, documented in the attached screenshot. I also ran the game without it to make sure there wasn't some other conflict in my mods, and it was normal.
It's almost certainly an error on my part, so here's a step-by-step of what I did:
1. Extract the archive for the Combine program
2. Place the .tga files for DH's scoundrel and scout into the INPUT folder.
3. Run the Combine program
4. Place the .tga and .txi files into Override, along with one set of model files depending on whether I want pouches.
Again, thanks for helping with this!