This type of design, was what I had hoped Phase One would work out on the XF, or at least follow up with it, as they made the 90 degree viewfinder removeable, (sure I know they have the other style that can be mounted).
But thinking more about it, probably won't happen to the XF, as you would also have to remove the finder screen inside the camera and that's not an easy job. The CMOS backs, would adapt pretty easily, just be in Live View all the time. With the power share tech they came out with, which works great, the drain on the back due to Live View would not be as hard.
Paul C