OK...banged on this a whole bunch. A few things were removed (the unbuffered mult, the Mutant Brain, the PipSlope, the 2hp mixer, the headphone tile, and the Stages) and much thrashing around ensued. The result is:
I treated this as a total fill-out, so that you can get some ideas. Although, it would be quite possible to assemble exactly that above and have a really stonkin' instrument.
TILES: Stereo IN, then the MIDI interface (freed up 8 hp in the 3U stuff), Steppy, a DuATT for mixing/attenuversion, a stereo (mono in) chorus/reverb/delay, then the Stereo OUT.
TOP ROW: Konstant Labs PWRchekr to keep an eye on your DC rails health. Then a buffered mult, as this borders on the edge of necessary due to new CV destinations. Odessa + expander next, then the NE oscillator, and after that, two MORE oscillators with internal quantization. Then the Moddemix (hence the two new oscillators...you can feed one each as carrier sources to a ring mod, or toss them at each other in a single ring mod). Also, note the quantization on the Twin Waves; it also has a clock input to step the quantizing, so you can use a single clock signal for that while it reads something like an LFO to create all sorts of tesselations. Veils follows for VCAs, then your MUM filter is after that for a mono voice. And there's a stereo mixer after this (which is where the voicing goes to stereo) which allows you to pan/mix all four of the VCAs if necessary. And out the other side of that, I put in a Bastl Ikarie, which is a rather neat stereo state-variable VCF to filter the stereo signal. Last is the Typhoon...note where that is, it's important later.
BOTTOM ROW: Pam's, then a Frequency Central Logic Bomb. Now, since you mentioned wanting to mess with generative methods, that Boolean Logic pair has the ability to generate many screwy/complex patterns from the Pam's, the Steppy, and really, all over the place in this. Then the two following modules are for CV "pickoffs"; the Comparator looks at two incoming values and then sends a gate depending on which signal level is where in relation to each other. And the Derivator is for reading CV movement and sending appropriate gates depending on that. Again, these can ALSO bounce off of the Logic Bomb. Erica PICO RND provides noise and other random outputs for the Pachinko...which is actually a smaller clone of Marbles. I tried using the Mutable module...but it was too big here. After that, a Batumi/Poti combo provides four LFOs, then there's a Frap 321 and Happy Nerding 3xVCA, which makes for a good pair of modulation alteration modules. Then a Quadrax with the Qx expander provides four AR or ASR envelopes. But by combining the LFOs and the EGs via the 321, you get even MORE modulation signals, and then the VCAs can control the amplitude of those. And then...a PROPER mixer. The Toppobrillo Stereomix2 gives you four mono input channels with CV over level, pan, AUX send, a CUE bus, mutes per channel, and a mono-send/stereo-return. Oh, and this is where the headphone preamp is now...PLUS it has the ability to be switched to CUE for spot-tuning, etc on the fly while the rest of the mix bubbles along. And this is why the Typhoon and the effect tile are in that general area...you can run them parallel via the AUX loop, or straight-through from the Stereomix2's outputs to the Typhoon and then to the OUT tile.
Now THAT'S an interesting build. It has generative functions (more than I've mentioned here, in fact), it can be MIDI controlled or not via USB, it has isolated I/O via the case's 1/4" jacks, and the whole thing's shot full of easter egg-ish functions from tandemming modules or functions hiding within modules. So...this is what you can potentially get when you mash the skiffs together and then looking at how to complement ALL of those modules with additions and a few subtractions.