Sooooo...where are the VCAs? And I suppose you could press the Pam's or the O&c into service for modulation, but that seems like a waste of what they're capable of. Attenuverters? Space for expansion?
Frankly, I would like to find out who's influencing people to make these pointlessly small builds...and kick their teeth down their throat!!! These clowns are causing people to waste a lot of time, effort, and money on builds that will not and CAN not function on par with the expectations of the people duped into making them. Thinking that something like this would be usable as a proper synth is along the same lines as thinking you can learn to drive on a tricycle. Yeah, sure, I get the "convenience" point of having something small, but that'll get outweighed VERY rapidly by the extreme limitations that using a cab like this causes.
I'd suggest getting VCV Rack and then trying to build an equivalent of the above in it. The problems should be glaringly obvious very quickly. Then start over with something like a Mantis (2 x 104) instead.