Went way further on this...and found some issues, most notably with the BBD module and a couple of others, all of which have depths of 60mm or worse. So instead of continuing with the same line of thought here, I opted to get a bit divergent and show what you can get to when you eliminate the Doepfer-primary constraint.
Yeah, pretty different, alright. For one thing, the layout is now properly consolidated, with audio on top (except for the FX send/return module) and control on the bottom.
Top row: This starts with the A-119. Then instead of the full-sized Plaits, I went with Antumbra's 6 hp clone. That then opened up more real estate, and so I chucked the Doepfer VCO in favor of a very satisfying double VCO from Noise Reap, their Paradox. This is sort of the "poor man's complex VCO"...the VCOs can influence each other via FM, internal regeneration, etc. Between that and the Plaits clone, I'd say that your sound generation is dealt with. I moved the Quad VCA/Mixer by these, which now lets you have CV over VCO levels going to the filters. And as for the filters, there's a neat complement there...the G-Storm Delta VCF is cloned from Korg's Delta (and Poly-61, plus a couple other Korg polysynths around that time) and gives you LP and BP functions with a smooth, paddy feel. The OTHER VCF, however, is a Nyle Steiner design, notorious for its strident and sometimes brutal lead voice capabilities. LxD is after that, meaning you could easily LPG the VCF outputs if desired, in addition to the "normal" LPG uses. Then I took this into full stereo via the Happy Nerding Panmix Jr., which then feeds to a Befaco OUT, providing isolated 1/4" outputs, headphone preamp (with a CUE input!) and master level control.
Bottom row: Disting, Doepfer Noise/S&H, and then Maths. After that, there's an Antumbra Dual VCA, a clone of 1/2 of a Veils, then a Shakmat Sumdif adder/subtractor, and a Tenderfoot 3-in attenuverting mixer...all three of these are intended to work together to alter/modify/mangle modulation signals, which makes much more out of the Maths and Quadrax than they have in of themselves. Next is the aforementioned Quadrax, with its Qx expander, and then Malekko's SND/RTN, which gives you CV over wet-dry balance to an external effects box.
The result is about $500-ish more, but also fixes your +12V rail issue by lowering the draw by about 140 mA. Plus, it has M0AR all over it...more VCOs, more VCAs, more filtering, more modulation, more manipulation potential. And compared to where this started, this is a HUGE upgrade in terms of functionality and sonic capability. All part of the fun that is Eurorack...there's ALWAYS other options out there!