Check out BASTL Softpop 2 - It has so much features in little space. -
Also make noise 0-coast
You could take on of them and build your system around it - just adding some utillities.
You can use them also standalone outside of rackspace - so you could take a smaller case only for utillities and pair it with them.
If I would start now from 0 - I would do it that way.
Otherwise
Did you check BASTL Ikarie? - also a nice filter with some tricks on it.
If you get BASTL Basil, you can also switch the firmware to the pizza VCO.
BASTL Pizza has many stuff like FM and waveshaping/wavefolding.
Or get pizza first and try out the basil-firmware later.
You maybe dont need an extra waveshaper/folder module then.
I have the ONA VCO. I like to mix the different waveforms with Befaco Percall.
You can also use it as LFO.
Ornament and Crime or Disting could also be an idea, to try out or to add different functions with little space.
You can use Ornament and Crime, as quad turing maschine, Envelopes, sequencers, quad quantizer and many more.
Greetings
Chris