I would like to have that feature, but some manufacturers wouldn't. Noticed how the citroen C4 only has plain colors? Or that any audi only has one avalable livery? One sollution is that it could be avalable to certain cars that the manufacturers have given permission to allow the use of a livery editor on.
While I find Cat mouse to not be realistic. It won't also work because of the stage design. The roads are way to tight for it to work. Now I will admit that it could work well on the rallycross tracks and maybe pikes peak, but I'm not really interested in seeing it.
And gymkahana should never step foot in this series again