If you want a full clean project with actual files, that would be more like a commission than anything else, because it require time

And second, you will only get the raw obj files and wont have the shaders required within the vrca.

At the end you will still to provide as much files as you need to make it run properly.
Hotswapping at this point would work better if you don't want to modify it. Otherwise, its easier to ask for a fully fixed project file containing the avatar rebuild with as many original files as possible than trying to ductape a reversed output.