I had some folks peep my build and threw around some ideas which radically changed the intial build .. but here it is here: ModularGrid Rack

I already have a Moog Grandmother, and a Behringer 303 clone, so this may interface with those devices, or I might just from it from a controller keyboard or my DAW.

In general I wanted to build something that was reasonable "complete" so I can get to grips with it all, and think about swapping our or adding modules further down the line ... cos that's how this works.

I wanted a couple of rather different OSCs to add some variety of flavour and then have the fundamental tools to sculpt those a bit without getting in too deep or spending too much straight off the bat.

This will probably end up in a case larger than the 84 I assigned it for future fun/updates.

Am I missing anything important, or are there any ways I could "improve" this rig?

I recommend a larger case at least 6u for room to add utility modules and a good sequencer.
Your setup would benefit from more modulation sources to make use of the audio in your setup. Something like a Batumi would be perfect.

dump the b-company vca - and get a decent quad cascading vca from a reputable company - veils if you can find one, an intellijel or a happy Nerding 3*vca - you will need more vcas so it's a better investment (especially the veils!!)

as @benscott suggested get a bigger case - you will need it much sooner than you hope/expect/think - tiptop mantis is by far the best combination of hp/cost/decent power/manufacturer reputation - the power in the mantis is way way better than the uZeus!!! plus you will avoid the waste of space that is a rack wart (power supply module)

I wouldn't put a compressor in a build this size - and probably wouldn't go with a dual adsr - doesn't the gm have cv and envelope out - I might add a voltage controlled envelope generator of some sort though

"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia

Utility modules are the dull polish that makes the shiny modules actually shine!!!

sound sources < sound modifiers < modulation sources < utilities

Input greatly appreciated!

I added the Butami and dropped the other LFO ... I'll add more as needs be later. Opted for a Doepfer VCADSR and dropped in Veils too.

Final case and PSU TBC. I started with this smaller size to ensure I had room to grow in a larger case but from a good foundation.

If you get the Batumi, I recommend getting the Poti expansion module for it as it opens up additional features without having to adjust the switches on the back of the module. For cases, Tiptop Mantis is great but I like the Intellijel 7u case as it has 1u row for cool additional modules that can make use of a small setup. For travel, I use my 7u Intellijel case.

Also check out the alternate Firmware for the Batumi.

One other VCA point: both Antumbra and After Later that I know of offer something of a "half-Veils"...two variable-topology VCAs in 4 hp with a summing buss that allows you to output them separately or together as a 2-into-1 mix. These can be VERY useful, especially for dropping into little spaces in your modulation complement so that you can futz around with modulation levels. Pair that with some small CV/mod mixer such as Frap's 321 or Tiptop's MISO, and you'll have a VERY powerful "modification core" solely for your LFOs, EGs, slope gens, etc.