Car sizes

So, I wondering. How would you change the size of the cars in the car designer. Would there be something like a scaling slider to decide how wide/long/tall our cars would be. There is a huge difference between small and big cars that I think are an important aspect of designing cars from a company standpoint. Like sedans, some people prefer nice big 18ft. sedans so they can have leg and cargo room as opposed to some people who like 12 ft. easy to park, mpg concious sedans. Also, vehicle size is also dictated by geography. In America, we like big cavernous sedans and in many European cities, they prefer small sedans.