Not to detract from Noah's / your integrated feature request, Har. In fact, I think that triggered controls (such as the Space F/R, or Pitchfactor's PitchFlex mode) can be a powerful source for creative application. Widely overlooked. You can add that capability over MIDI – to any of the 'Factor boxes – but it's going to involve some specialized hardware (or software, for that matter).
I noted on another thread that you are a "former MPX1 owner". I happen to use mine largely as a MIDI controller. Any of its Internal Controllers can be assigned to CC numbers, and transmitted over MIDI [MPX-1 Out -> 'Factor In]. That includes the A/B switching [Lexicon's original "morph"]. I'll use it – for example – to morph intervals and 'chord' inversions in the PF's diatonic modes. Notes glide in & out at different rates; depending on the 'morph' settings and the distance between targeted intervals. Beautiful – or jarring – effect; depending on which parameters you 'morph'.
It can be initiated from any external switch, internal controller, MIDI, etc. Now, the A Rate / B Rate in the MPX-1 are logarithmic, and time-based. So there is no 1:1 correlation of values between 100 (less than a ms.) and 0 (over two minutes). The workaround for 'tempo sync' would be to trigger from another, synchronized control (LFO, etc.), and adjust the A/B Rate controls meticulously.
The MPX-1 wouldn't be your only option. Maybe something along the lines of a Moog MP-201 control pedal would allow you to trigger a one-shot LFO from one of its switches. Match the RCV parameters in the 'Factor pedal, set the limits, and you'd be able to morph through any parameter, in either direction. Any MIDI LFO that has shape/pulsewidth, waveform, or offset controls should let you select among various curves, directions, and the length of morphing.
I'm sure that there are other MIDI solutions, but I concentrated on "hands-free" and "Can I lug it with me (easily)?" A small hardware sequencer might be an option. If you have one hand available, or are working in a DAW environment, the options really open up … exponentially.
