Notwithstanding the fact that I recently bought the Acratech, it strikes me that the fundamental design of all the panning ballheads I've seen is flawed since the panning head is on the bottom of the head. If they just moved the panning plate to the top, that would solve the problem with no new gear required.
I have an old novoflex magic ball and separate pano plate, just screw the panning plate into the top and the QR clamp to the panning base and you've solved the problem.
Really Right Stuff makes one... the PCL-1 panning clamp for $235. The only downfall is when you want to point the camera up or down, and still be able to pan on a level plane.