In terms finding the parts...I'm pretty sure I could work with this palette of tools:
Of those, these have a lot of promise: http://www.yakima.com/shop/racksyste...bolt-toploader
Agreed with the weight limitation - I wouldn't be putting heavy stuff on there. I race bicycles and live in the city...many of us carpool out to the races. Everyone puts the bikes on trunk racks but you don't really ever want to keep your $2,000 wheel set out there in the wind still on the bike laterally, especially if they're aero and carbon. Believe it or not, trying to fit four wheelsets in a car with four people and all their gear is where it gets difficult.
So my thought was to put one or two of those yakima bars on the trunk as a wheel rack so that the wheels would be pointed in the same direction as travel (yakima makes similar concept for roof racks). There'd never be more than like 10lbs on it.
I know what you're thinking - just get a roof rack. This seems stupid but I can't tell you how many 6K dollar bikes I've seen destroyed atop a roof for one reason or the other...when you do this 30 times a year it's pretty easy to forget you have something atop there and go under some small country overpass or a car port or something. And I have a bit of a tendency to be absent minded before big events like races.