I wouldn't call 200 BHP, 186mph top speed, 0-60 in 2.5 secs "little return" Max...
I guess that depends on who you ask. Especially if you are comparing to a C14 that already has a replacement exhaust and Ghul flash or PCV. And peak HP does not describe a whole power curve.
* The bike is heavier and the shaft drive will eat more power.
* You will NOT end up with 0-60 in 2.5 seconds with a ZX engine on a C14.
* The aerodynamics will be different, limiting speed on the C14 (and top speed is a "who cares" for most non-track drivers, anyway).
The main advantage of trying to put a ZX14 engine in a C14 [instead of a turbo] would be that it might be possible to do without any fabrication or custom parts (if the transmission would bolt up to it). Most of the difference remaining between the two would be the head and intake. The bore/stroke is already the same, so at most, a head swap would make more sense.
Again, I am guessing it would cheaper and more effective to add a turbo to a C14...