Pretty simple concept that seems very achievable-
A pedal with 2 FX loops- according to the envelope of the input signal, the output will 'pan' between the first loop to the second, or it could 'fade-in' the second effect, or do either with a dry signal.. You could also control it with an expression pedal obviously or even LFO voltage controlled!
The possibilities i could keep throwing off of my tongue could take paragraphs, and most of them seem easy enough, even at my level of experience with designing circuits.
loop 1: some fuzzy fatness
loop 2: octave up pedal with chorus reverb
You strike a fat fuzzy note, and a bright shimmery atmosphere creeps in or: (fuzz) panned to (fuzz + octaved dry bass) not that the latter is NOT fuzz into octave. anyway...
loop 1: Iron Ether Subterranea -> envelope filter
loop 2: LFO based modulation (Polytope anyone?)
After that badass swept fat pulsewave attack, the LFO warbles away, putting together a new level of synthesis options
note that this would be achieved by The Subterranea staying in the signal path, and that the panning would really occur between Subt>out / Subt>
Ill draw up a 'knobs and switches' brainstorm for fun in a second, and if anyone is interested in experimenting with the ideas, I'll post some circuit ideas and we can brainstorm, because I'm not finished being dumb at electronics yet