George, how about...
-A dedicated button for "On Bass" chord recognition (or a user-definable button that can be assigned this function)
-Mark and Jump buttons (and the related functionality) to play along with MIDI files
-Dedicated knob to balance "live" vs backing tracks
-At least one "assignable slider" (or allow the modulation wheel to be remapped for this purpose)
-Software support for the MFC-10 foot controller (or better still a new, smaller MFC-6 foot controller)
-Larger screen, say 640 x 480

Thanks!