'69 Mustang with a rumble seat -OR- Why I love Barrett Jackson

At the Barrett Jackson auto auction today there was a 1969 Mustang with a rumble seat which supposedly was a rare pseudo-factory option.

From the Barrett Jackson website:

"It was a "Blossom-Time" sales promotion offered only during April 1969 to certain Michigan dealers. Documented by 2 different magazine articles, it is still un-certain exactly how many were done."

Why don't more cars have a rumble seat option? I'd be able to justify a Miata or S2000 if I could carry the occasional (fair weather) third or fourth passenger.

I'd bet there is a market for aftermarket rumble seat conversions for modern sports cars. It should be fairly easy to implement; design hinges to allow the trunk to open forwards for normal use (with seat cushions removed, of course), or backwards for rumble-seatage.

I mean, who hasn't dreamed of a four seat Corvette?