You probably want the faster AF of a pro body for shooting sports. Of course, a 'Blad is manual focus so that's a whole different type of shooting. There are motor driven MF cameras, but 2fps is very fast here - and nothing compared to DSLR's or 35mm SLR's.

DSLR's crop the edges off the frame - they don't alter the focal length. Problem is that your fisheye not only won't have that wide angle of view anymore, but it won't look much like a fisheye either (most distortion is in the area that would be cut off).

Here's another one to throw at you - Nikon D2H with their 10.5 DX fisheye. The camera (if you can still find one) is $2K, lens about $600. The camera was just replaced by something that's not a huge upgrade so they cut the price from $3200. It's 4mp and reportedly is fine for double-truck magazine images (two pages wide). I haven't shot one but have handled it and it feels great. The 10.5 fisheye was developed especially for Nikon DSLR's. With their software, you can take the distortion out and get about 120 degree angle of view or something amazing like that.