The ability to skin the internal bodies of cars?

I feel it'd help for some skins. If you look at the Beater Covet, it's all worn on the outside but where the wheel wells are and stuff you can see the body is a bright, shiny red, and it kinda ruins the look.

 

I believe it would require a uv map of the inside too, which is impossible.

 

Maybe not impossible per se, but it would be a huge pain in the ass

 

SuperAusten's skin for the beater moonhawk in WBIMP has skinning on the underside, you might want to take a look at how he did it.