I'm also wondering if the complete tail assembly including subframe could be made to fit onto the frame of the FZ6.
Wish I had lots of money then I'd try it!!!
Edited to add... with an additional thirty seconds or so worth of thought, of course the answer is clearly a no! The FZ6 is set up for an underseat exhaust, the FZ6R isn't, so if someone did do the transplant they'd have to cobble together some sort of side exiting exhaust system for the FZ6 and that would increase costs dramatically.
And for the record, having listened to the stock exhaust on a FZ6R (Or Diversion, as they call it in the UK) there would be no way in hell I would be prepared to lose the undertail exhaust, the R sounds like a fart in a beancan. IMHO.