I would love to get back into kayaking. It'll be mostly renting for me, as I've yet to figure out a way to strap a kayak to the Z4.
Just buy an inflatable, like my wife's. Or the Feathercraft Aironaut. Compresses to the size of a small suitecase, and takes 5 minutes to set up.
Seriously, though. I hear you. Two seat roadsters and kayaking are tough to reconcile. Especially when you consider all the other gear you need - paddles, spray skirts, a change of clothes, life jackets, lines, and so on.
I don't know about inflatable things on the water. I used to have an air mattress...doesn't inspire confidence. And I'm not too strong a swimmer. I won't sink, mind you, but I can't hold my own against Michael Phelps.
When I went last, it was just the boat, the paddle, and a life vest. I almost didn't want to wear the vest, since I can swim, but someone told me of a time they lost it and hit their head on a rock. Without a helmet, they'd have been knocked unconscious. Can't swim very well if you're unconscious. At least with a a life jacket, you'll float. Looking cool definitely is second to not drowning.