This would indeed be a nightmare to UV, well done though!

a guy I know used to make a Gundam fan game, I'm still amazed he could deal with the UV maps that caused.

Do you reckon there's a way to color code the UV?
Say you painted the different parts, would it be possible for that to transfer over to the UV?

It would be incredibly helpful if you're looking at a rendered model as a reference as you create a texture for it.
I honestly don't know, UV unwrapping and texturing is something I haven't quite gotten to yet, still focusing on making decent models and armatures.

Blender exports UVs with the material color, I've also seen an exporter that put some sort of rainbow colors on the UVs so you could easily see which is which as long as you look at the model at the same time. I don't think it'd be terribly hard to figure out though, most of the pieces here have fairly distinct shapes.