What do you mean by “… difficult to control changes …”? I’d like to help out here, but I’m not exactly sure what you’re after. I use the Diatonic and QuadraVox algorithms quite a bit, as well as the other ‘static’ pitch shifters.
In fact, I can’t seem to let go of my PitchFactor; sharing the same ‘board as two H9’s. I cover simple harmony changes with an aux switch or expression pedal. For more complex or sequential harmony changes, it’s foot-switching over MIDI, or an EHX 8 Step Program / sequencer.