Interesting. I’ve had the Bass++ on my “do someday” list for a long time, though with mods. Including the separate envelopes for pitch and amplitude* and a minimalist wave shape control, as discussed in this thread.
I hadn’t considered exponential CV for the VCO and am not sure how useful I would find it.
I would likewise omit the master volume — an output attenuator, not something I generally want. I’d probably keep the shell volume and impact tone controls. Of course, I build Kosmo and have lots of real estate for knobs. And on PCB, so the constraints of stripboard aren’t relevant to me.
* By the way, the Barton Analog Drum (which I’ve built) has some distinct resemblances to the Bass++; it does lack the impact component and some of the controls, but it uses two envelopes.