Okay everyone, I fixed the problem. When you go into SP and see that your model is invisible, you're going to press ~ to open your console.
You then should have a whole bunch of vertex errors that say the same thing show up.
For example: The vertex error says "Male_5" in it. Exit GMOD, go into your programs, Username/Garrysmod/garrysmod/models/humans/group03(or group03m) Delete all six of the "Male_5 folders".
Then, open up GMOD and wallah! Whatever invisible model that had the "Male_5" in it's vertex error should no longer be invisible. Even after this, you still have all the TnB models for the default rebels! Except now, they're no longer invisible. I did this for all my rebels that were invisible, and they all work perfectly fine. :3