What have I missed? There are a few few modules I feel strongly about (like the rainmaker) but there are others I'm not sure about. Which one would you suggest me to drop/replace from a starter kit?

Hmmm...the ideas are there, things just need tuning-up. First of all, great sequencer...but where's the quantizing? Sure, the Chord has some quantizing capabilities, but after checking its docs, they relate to how it deals with harmonizing the incoming root values, not determining the actual incoming pitch CV for the root. So you'll still need something to quantize that root value in its own scalar context, THEN the Chord's quantizing-to-chords will have something to work with.

VCAs. Two really isn't enough. Yeah, I know they're not sexy and all, but several more are needed for both audio and CV processing. Maybe lose the Pico drum modules for those?

Can some of these modules be smaller? For example, the Modor Formant Filter and the Limaflo Motormouth are similar things (formant filters) but the Limaflo is 4 hp smaller and saves you about $150. Since you're doing a lot with Erica's Pico series, I don't think I need to go on much about jamming functionality into small spaces. There's not any way to sub out the biggest thing here (the Rainmaker) but I think a bit more digging around will turn up ways to regain some usable hp by switching in smaller variations on some of the chunkier devices in here. Also, I'm pretty sure that you can cram in a MIDI interface with more channels and/or functionality in the same 6 hp or less. So in all cases of everything, it might be an idea to go back and retune for space; even the Picos might be able to be supplanted in some way by larger modules that offer more of the same function in spaces not too larger than a few Picos take up.

This setup also brings up another point: if you're just starting out in modular configuration, always be prepared to make several initial sketches of the same basic idea, then distill those down into a case that's actually LARGER than what the configuration calls for. Blank panels are cheap, plus as you actually work with the physical device itself, you're going to be running into "I need it to do _______" situations, and at that point, you'll want empty space to jam more modules into. Even after some 40-ish years in electronic music, I'm always re-evaluating what happens in my layouts (which is what makes MG so useful!) and fine-tuning, especially because the Care and Feeding of a modular synth is spendy, and you need to make decisions you feel will work with the result feeling very 'instrumenty' from square one. It's definitely not a cheap commitment, so making mistakes and fine-tuning constantly (even down to trashing whole configurations in favor of something with better 'flow') is a MUST. Thankfully, we've got this resource!

Thanks a lot for the thoughts! Quantizer is clearly something I had to think of! Getting back to the drawing board... :)

What Lugia said.

The Z8000 sequencer is huge and the outputs are unquantized. Perhaps look into an Ornaments & Crime 8HP multi-function module. The price is about $250US and you get two 16-note sequencers that won't require a quantizer. It also has a dual quantizer function in it as well. If you pair that with an Expert Sleepers Disting Mk4, you get a lot of functionality in a little space. Some functions overlap, which can be an advantage. You can always add the Z8000 to a larger version of this system and your O_C and Disting will find other uses... they won't become redundant.

Look into the 1010 Music Bitbox if you're going to have on-board percussion. It's 26HP if I remember correctly and $600US. But you won't need all of those sample-playback percussion modules and won't need any additional modules to mix them. It also has easy loading alternate firmwares (free!) as a synth engine or an FX box. You can also record and loop any audio signals from inside your modular (it doesn't record DC). This will let you record the output of the RainMaker if you have some sort of awesome ambiance going and want to buy-back some of your modules that went into making it.

A clock source or divider is also a must (IMHO) for starting a system. Pamela's New Workout or a Temps Utile would work out well.

Also, the Rainmaker and Erica DSP have stereo outputs. You'll want some sort of mixer to take your mono signals and stereo signals and combine them... the same for any stereo samples.

And last, the Batumi has an expander called the Poti. It's 3HP. It will give you a lot more functionality out of the Batumi in terms of waveforms and sync/reset. You HAVE to have it IMHO.

Another observations is that you use many tiny modules (2hp and Pico). I am sure there are many different opinions about this (and I would be very interested in hearing Lugia's view), but I think it can be a problem, because: 1) they are hard to work with (tiny pots, cables too close together); 2) they are typically not fully featured compared to full size modules; and 3) they are relatively expensive for the functionality you get.

If you look through the list of the 100 Top Modules, rated by users, there is not a single 2hp or Pico module on this list.

I suspect you just want more functionality than what really fits in the case, and the easy fix is to just start with a bigger case, so you can get this functionality in regular sized modules.

I don't mean to say that one should never use tiny modules. They have their use, typically when you are running out of space and need to solve a particular problem. Of all things, I ended up with a 2hp, 3:1, because I needed switch, and it is great. But unless you have a particular reason, I don't think it is ideal to use them extensively from the beginning.

My take on the 4 hp and down world is that, when they have a function you need and space is limited, they're a blessing. Take Erica's mixer modules, for example; that would be about as small as I would think could work as a simple mixer. But when you start getting into shrunk-down versions of modules that have major functionality in their full-sized versions, I'm a lot more skeptical. For example, 2hp is great for things like their dual VCA, as you don't adjust a VCA all that much, and there's nothing complicated there: in, out, modulation. But I wouldn't consider their version of the Turing Machine to be a contender against a fully-blown Turing Machine, as there's a lot missing that really makes that module (module group, in truth) what it is. Small also works as "hole-fillers"...need an extra basic VCO to mix against a bigger, more featured one? Sure, drop in an Erica PICO if you've got 3 hp to spare. But I'd never use one as a primary VCO unless I was building something in the size of a single Moog 60 hp skiff or smaller.

And then there's manufacturers that specialize in small, aside of 2hp of course; one that comes to mind is Ladik. Ladik has things that fit in 4 hp that really don't exist anywhere else. In such cases, those ARE your primaries, and there's nothing wrong with using them to get that extra bit of functionality. One just ignores the fact that it's in a small footprint. One other one that comes to mind, also, is Konstant Labs' 1 hp power checker; if your cab has no power rail indicators and you do happen to have an extra 1 hp free, then I'd call that a "must-get". Slip it in on a row end, and you get valuable rail voltage info...again, tiny as hell, but tiny works in this case.

Otherwise, yes...if we're talking about something that needs a lot of interaction, like a VCF, then small probably isn't the way to go. But again, different builds and/or different users call for different things, and there's not really a hard and fast rule about size. If you've got Trump hands, then PICO might be the way to go!