"I still contend that technology is such that a FF body can shoot 8-10 fps and that recently the performance limitation has been imposed by Canon to protect their flagship, not the availability of technology. EOS film cameras could shoot 10fps and those bodies had to advance a film roll so I know it's possible with digital."
FF is not the issue but MP count is, a recent Canon technical piece stated that there is a problem with the sensor at 18MP and 10 fps, each time an exposure is made the sensor is 'reset' wiped if you like, the technical problem is in resetting the larger pixel counts. Failure to do this effectively builds a series of ghosts of previous images, which gets worse as the number of images in a burst increases.
Your ideal camera is very very close to the 1D MkIV. 16.1MP isn't very different to 18MP it does 10fps dual card slots and clean Iso 6400 the only compromise is the Aps-H even the price is about right if you're quoting in Â£ notes!
As far as I remember, it was an issue of a FF, not MP. That was the reason to put APS-H in 1D4, they could have made it FF, if the problem was pixel count. Nikon's fast FF shooters can't shoot more than 9fps in FF mode, only in APS-C, because of this as far as I understand. But as it goes so far in technical details it's more based on what one read on forums and stuff, so we can't be sure.