Classically, sexy women and cars are quite often associated, possibly due to advertisement. I wonder why there are not more adult games that combine racing and adult stuff.
If you consider adding customizing the mc, you might also give ability to change her body size. Like make her skinny or very fat. Since I assume the engine does the rendering you could embrace this to a certain point. I remember a game where the character got weight or skinned down by eating too much / too litte in the game. I think it was Fable. That was a cool feature. It was silly, but funny.