tedolf
Forum Pro
Because it would be huge, heavy and have gigantic lenses. The Fuji X-Pro is bad enough and it is only an APS size sensor. Moreover, it would have the miserable 3:2 aspect ratio sensor that requires cropping for almost every popular print size.
Finally, it already exists. It is called a Leica M9. Sony makes one too.
Now, if you took the old film Pen-F body and just put a half frame sensor in it I would buy that in a heart beat!
Tedolph