It does sound unlikely. Why on earth would anyone use a crop mode on a MF camera? You get a MF camera because of sensor size then why not use it? Does not make sense. However, if FF is considered "full" and aps-c is considered "small" then medium format might be aps-h? But then again, why keep that format around anyways? Better to develop less sensors and do them better as competition on sensors are harder than ever. No. If I would spend money on a MF cam I would also spend money on one or two great lenses built for it instead of cripling it with croped lenses.
Well it's not as crazy as it sounds.
For studio work I use two lenses, on the H3dII-39 I use a 100mm 2.2 with a 1.7x TC, I also have an 80, which I don't use and a 35mm for landscapes.
My canon kit though has 10 lenses.
So a MF body with an EF mount would be cool. I could buy the body, then expand my lenses. a bit like how you can fit a EF lens to a crop body. It doesn't use all the lens but you get used to the L glass.
But if you can remove the back and send it to a Haselblad / Mamiya or Phase body Canon will sell them by the bucketload. In fact, I'd go so far as to say they'd dominate the market in less than 12 months.
The only thing Hasselblad's H3D body and sensor has over the 1DX is 39mp, 16 bit files, no AA filter, and Hasselblad glass.
But my max useable ISO is 200.
Imagine what it would do to the MF market.