I can confirm that ganging parameters on a knob, or in my case (H9000R has no knobs), to a MIDI expression pedal, works perfectly.
In fact, I wound buying a H9 in addition to my H9000 mostly because I wanted to replicate the ribbon presets as they capture the intelligence of a preset user. I mean, a H9000 complex preset with many controls is challenging to tweak to produce pleasing variations.
In fact, it would be nice if Eventide could somehow offer these “ribbon presets” so that H9000 users could include them into their H9000 MIDI controls without having to buy a H9 *and* re-purchase algos that they already own on their H9000. But I love Eventide and I don’t mind giving them some deserved incremental business.
Back to the problem at hand, the main issue is that the 4 FX Blocks in the H9000 cannot be connected internally. I had suggested years ago upon first look that it would be a crucial functionality, but it may be very difficult to do for hardware reasons.
What I wind up doing, as far as blending FX chains, is to connect “externally” my H9000R to a Switchblade GL unit. It effectively allows me to include my H9000 in my guitar rig as 4 stereo “analog in/out” or “virtual H9” units, and I can do any cross-fade or blend from the Switchblade and control all cross fades via MIDI expressions.
It clearly would be great to have the ability to blend FX chains in the box of the H9000, but I don’t know that it is necessarily as trivial task.