Its your choice, but the way i imagined you were going to do the STIG was to have him standing next to the car with his arm leaning on the roof. To make him look cartoony you could make the head larger in comparison to the body and emphasize the visor on the helmet. Make it really reflective. So basically you need a cartoony human shape with a large head all dressed in white with a white racing helmet on. I think your friend who does the sketches for the car might be able to help you design Tinpau style STIG. Those were my ideas, do what you want with them, and good luck with it. Cant wait to see final renders.
Andyflag: I can mold fiberglass, gokart is a great idea, i was going to attempt an approx 1:24 scale model out of resin. Maybe in the future if i have more of a budget i could make a gokart. Whatever it is i make, i shall post it here.
p.s. making fiberglass molds aint that hard to do, if you want more info on them pm me.
Well I was supposedly working with someone on using some of my designs for toys, but alas, he was full of it and never came through....he wasn't using my designs as much as using me. But I certainly would love to work with some toy company or someone who could make and sell these as toys or kits.