After much beardstroking, guru #127 replied:
"If you want to replace only the model and textures for your own use, it would be easier to replace the original model from "Data3d.pbo" and put the textures in a .pbo in your "Addons" folder. You can use one of the .pbo unpacking/packing tools for that.
Modifying the config can be a bit of a headache. And from what i've heard, in MP, servers can detect a modified config and might not allow you to join. Cause if everyone would be permitted to tweak their configs, that could lead to cheating. Peace"