Thread: The Rack of No Rhythm
You may want to consider swapping one of your three VCOs for another VCF to compliment the Polivoks. I would, in addition, swap the Shuffling Clock Multiplier for something more useful such as an LFO.
To run a guitar (or most anything else) through a synth I would recommend the Doepfer A-119 External Inpuit/Envelope Follower, perhaps coupled with an Inverse/Offset Attenuator.
Regarding the construction of my own powered custom Euro-rack modular case(s), I plan to use the Z-Rails, Bus-Boards and Power Interfaces manufactured by TipTop Audio.