Here ya go... https://www.modulargrid.net/e/ai-synthesis-ai008-eurorack-matrix-mixer Even fits in the hole left by the o-scope with a couple of hp to spare.
Still seems like there could be some improvement here, though...give me a bit...
Haw!
OK, so sue me...I "cheated" a bit by using an Intellijel Palette 104 cab for starters. This gives ALL your I/O jacks, mults, MIDI via USB and power right off the rack, though. And this'll be a common theme in this build; why put in single function devices when you can double up your functionality in the same space?
Tiles: MIDI interface, Noise Tools (noise, clock, sample and hold, slew limiter), dual linear VCA, QuadrATT, Multi-FX, Stereo out.
3U row: Pam's (eight channels of clocking and/or sequencing), Wogglebug (fun with randomness), Batumi + Poti (4 LFOs), Zadar + Nin (4 envelope gens), Gibbon ALAK (4-channel step sequencer), 2 x Klavis Dual Waves (dual VCOs with internal quantizing), Veils clone (VCA submixes to the VCFs), G-Storm Delta VCF (multimode w/ 2-ch input mixer), G-Storm SH-101 VCF clone (LPF, also with 2-ch input mixing), Antumbra 1/2 of a Veils clone VCAs, Happy Nerding FX Aid.
Now, take a closer look here...there are very few single-operation modules in this. Everything in the 3U row (except the Wogglebug and the FX Aid) either does multiple functions, or can output multiples of the same function. The tile row lets you move the attenuator/mixer OUT of the 3U space, along with letting you use a number of other things that you also wouldn't necessarily have room for in the 3U row. And likewise, this is capable of operating in a true 2-voice mode, or one massive single voice with FOUR oscillators. Four channels of CV sequencing, eight of trigger sequencing and/or clocks, plus a NINTH clock as an overall master in the Noise Tools. Two different FX paths (mono-to-stereo and true stereo), two different VCFs that can also sum down two VCOs each (via their VCAs, natch), and so on. Relying on additions such as tiles (when doable) and multifunction modules allows this...even in 104 hp! So, yeah...you CAN build a single row skiff that's VERY workable, it just requires a very different "eye" for the right devices, and a very different mindset about how to pick the right modules as opposed to a larger build.