I always thought that a modular Stage would be great. Two panels, but instead of Piano, Organ Synth, they could have swappable boards so the user could define what what they wanted based on their need. I never, ever need more than one piano or organ, so the configuration you mention would be my choice, one piano, one organ, 4 synth. That is why I have the Stage 3 and the Wave 2. Of course, this would require major hardware changes.
-dj