I have been playing with the Mothership Guitar Synth. One very cool thing is their approach to ring modulation, which uses a pitch-tracking carrier wave that can be tuned, and then applies the ring modulation effect consistently with the underlying pitch … i.e. you can play a C scale and get the ring-modded pitches you would expect to hear in the C scale with comparable tones. To me, this is musically how all ring modulators should work, because it is musically intuitive.
However, the problem with the MGS is pitch tracking, namely glitches that appear in the upper register notes. My experience with Eventide products, and what I see in the PitchFactor demos leads me to believe you have excellent pitch tracking. What I suggest is you feed the pitch tracking output into ring modulation algorithms to create musical ring modulation. The input pitch could be shifted and the offset tuned or fine tuned for the desire ring mod tone. It would also be nice to offer several types of carrier wave (sine, square, saw, etc), and perhaps even the original modified signal. It may even be interesting to see how other Eventide modulations work as the ring modulator carrier wave. This could get REALLY interesting!!!