Building a car from a pile of parts...  Sounds familiar!

http://www.businessweek.com/videos/2013-10-16/the-first-car-you-can-build-yourself-dot-in-an-hour

It's open source; anything is possible!

I think these would be fun! I bet they will become a registration nightmare. It won't be impossible in most states because you can register it as a home build, but each state will vary and that will make it a little tough. Still an awesome idea