Race on, Race 07, WTCC the Game, and any other expansion based on the Race 07 game use the same files and same location for add ons and skins. You can see this best by adding a skin. If you own all the expansions, the skin is available regardless of which icon you used to start the game as long as you choose the class and car type that go along with the skin.
I am not sure who started using the "Default Int Driving suit.dds etc in the ini file, but there is nothing in the official readme file about using those so they should not be in the ini file. The only files that need to be mentioned are ones that are used specifically for the skin in question. If the ini file mentions an image, make sure that image is in the folder for the skin. If there is no mention of the image, why make up something that the game will have to run around looking for?
Good luck with the issue. Hope you get it worked out.