Not so sure about publicity really, if it is mainstream media, they won't probably mention it at all, just think about the whole deal, he will be in the spot light, I wouldn't be suprised if he claim the design as his own.
In terms of publicity in the racing circle, I already have two clients in WTCC and that alone weighs a lot more than someone who is a weekend racer, hence it doesn't seem like that big a help if you think about it.