+1 on the Mantis, as usual. And in fact, this build shows why:
The current build here is 1/2 of a Mantis. You'll notice that all of your modulators takes up about half a row, the voicing takes the other half. That's not TOO bad...but it means there's no room for FX, submixers, etc etc etc. BTW, that layout is cribbed from the Steiner-Parker Synthacon: modulation left, voicing right, but it avoids the "mix at center" issue that the Synthacon had. Plus, one other immediate point: the UliPlaits can be swapped out for pretty much ANYTHING that's smaller; you don't have room for a single 16 hp oscillator (with extra bits). There's barely enough room for the Maths, but it's far harder to "shrink".
Additions are: Doepfer A-154-4 quad LFO. There is the one on the 100M clone module, but I'm not all that jazzed by that module anyway. It takes up too much space for what it is; you could easily drop in a Xaoc Batumi and Zadar if the B. 100M and the quad LFO weren't in there, and that would give you four LFOs and four EGs. That's a little outside of the scope of this exercise, though.
Tenderfoot Ease and After Later DVCA. These are a (bare minimum) modulation manipulation core. These allow you to vary and/or invert modulation signals, place modulation under VCA control (VERY useful!), and in essence make your modulation sources...uh, more modulation sources.
4ms Listen I/O. This not only handles the drop from synth-level to line-level, it can also do the opposite in its input section, meaning that you can use the synth to process incoming audio.
So...it's workable, you can make it behave like a very basic monosynth with some extra trickery inside. It's still missing stuff that you would have space for in a Mantis, though.