I think the big attraction of a 4 seater is that it actually has space to carry "stuff", which makes it much more sensible for touring, as opposed to competition.
Tarka is wonderful, but she lacks anywhere to put anything, other than a small space to behind the seats and a rack on the back. I would love a 4 seat body on a new Plus 8....probably not possible because of the suspension intrusion, but a "Shooting Brake" or pick up truck rear end would work, especially as there is no spare to be concerned about.
Go for it, I think you have found a gap in the market.
