One of the big three (I think it was GM, not sure) was planning this exact thing back in the late 90s.  They'd pack an entire drive-by-wire electric car in to a giant skateboard, and then they'd simply be able to sell different interior/exteriors that would be mounted on top.  Then they could focus all their development in to three or four actual drive platforms.<p>It was a great idea, and had they stuck with it I'm sure we'd be close to using it by now.  I expect that batteries ended up being the torpedo though.