On the waiting list for an XD. I had a v1 and miss it. The two switch version is much closer to the perfect filter for me. That being said if we are putting together a “Xerograph Super Deluxe“ wish list let’s add lfo with selectable wave shapes 
Great post, @movinngruvin! I've never been very good at coming up with metaphors to explain this stuff.
I definitely hear you on the "XDD" - having knobs for attack and decay and the effects loop would be cool. Probably means a double-sized enclosure, as you say.
Can you tell me more about what you had in mind with the bolded part? The EXP knob limits how much the control signal from the expression pedal can offset the filter's cutoff frequency. It sounds like you want it to instead/also control the maximum frequency that your playing dynamics can sweep the cutoff up to, but that's effectively what the Sensitivity knob does.