I don't fully buy this - if you optimized for aerodynamics and safety you'd get cars so far outside the aesthetic it would be ridiculed. No-one is making fun of the new USPS trucks for lack of fuel efficiency, they're saying it looks like a platypus. I can see a weaker version of what you're saying, that the intersection between the aesthetics a mass car market would accept and an acceptable fuel efficiency/safety yields a very narrow design space.

Not really sure what you think would change if you did this?