Well, let's see...part of the problem is that you're rather dependent in this build on BIG modules...which take up quite a bit of space. Instead, work on how to accomplish the same thing in LESS space.
The Strymon, for example...there's not an exact replacement in stompboxes, but the ability to USE stompboxes might be very much of use here. So if the Starlab costs $650 (it does) and robs 28 hp, it might make far more sense to use a couple of Strymon AA.1 modules...which then allow you to connect two different pedals of all sorts. This also keeps you from being too dependent on that single module. Tossing it also opens a lot of room; even with two AA.1 expanders, you still gain 20 hp.
Another problem is the Akemie's. Algorithmic FM, done right, involves a number of envelope gens. So not only would you have all that space taken up by the Akemie's itself, you'd ALSO have to have space for a quad function gen such as an Intellijel Quadrax or a Tiptop/Buchla 281t. In short, a FULL Akemie's implementation would take a PILE of space. And 2hp's stuff is OK...but poses a serious ergonomics problem when you start stacking them up, making the controls too tightly spaced for easy use.
As for the chord pads...if you try and implement that in a test build here, you'll quickly find why polyphony and modular can be a really bad mix. You're better off getting a real polysynth; I suggest the Modal Argon8, myself...not too spendy, plus the synth engine is a wavetable BEAST.
Anyway, the case is right...we often recommend Tiptop's Mantis on here for first builds because they're solid, they've got decent power, and you get 40 more hp in a 2 x 104. Let's see what I can cough up here... (several hours later...)
OK, this should work...and amusingly, this full cab only costs about $300 more than the previous unfinished one.
This has everything you'll need for a "core system". Anything from that point is additional. And there are some real surprises in here...
TOP: Starts off with an audio input, with envelope following AND an onboard P-to-V converter. This allows you to control things from any monophonic source. Then for the "main" oscillator, I went with an SSF Zero Point Oscillator. This has a lot in common with Intellijel's Rubicon2...except for the space required. After that are two Klavis Twin Waves mkii, which are dual wavetable oscillators with internal quantizing. This gives you a total of (technically) SIX oscillators. After all of that, a Void Modular Hexagram crams six VCAs into one module, with a "breakable" mixbus so that certain sources can be isolated if needed. Then for VCFs, I put in a Tiptop Forbidden Planet and a G-Storm Delta VCF. The former is a reproduction of the infamous Steiner Synthacon multimode, with HPF and BPF capabilities that can turn basic lead lines into something aggressive and in-yer-face. But the latter filter is much calmer...an SSM design based on the VCFs in the Korg Delta and, later on, their Poly-61. A Veils provides VCA control over levels being sent to the Alyseum Q-Mix, which is a four-channel pannable stereo mixer. For effects, a Frequency Central Stasis Leak gives you mono-to-stereo versions of tap tempo delay, stereo chorus, and reverb, and then Mutable's Beads lets you screw around with the entire mix via its granular processing. Last up is your output module, which has transformer isolation for the stereo outs as well as your headphone preamp. So, that's the "voice" path...leaving only...
BOTTOM: Konstant Labs PWRchekr starts things off so that you get a visual readout on your DC rail health. Then Pam's, followed by a Qu-bit NanoRand v.2 which gives you a sizable artillery of random sources, etc. And then after that is a very interesting pair of modules from Stochastic Instruments: their Stochastic Inspiration Generator plus the expansion module that gives you independent control of all four of the SIG's tracks. This is a melodic pattern generator that uses stochastic processes to generate melodic lines, with the occurance of each pitch being weighted by the chromatic set of sliders. Following this is SSF's awesome little utility module, the Tool Box. Then we get into modulation sources, starting with a Xaoc Batumi + the Poti expander, Maths, and a Quadrax/Qx pair. But as for the small modules after the Maths, those allow you to manipulate the behavior of modulation signals...so there's a Frap 321 for mixing/crossmodulating/offset generation/and so on, then a Happy Nerding (stay safe over there, dude!) 3xVCA for a trio of linear VCAs to control modulation levels.
Now, this seems a lot more sensible. Not much in the way of oversized modules, and the functionality is REALLY jacked-up from what was there before. And like I said, it takes the price of the previous unfinished build and only adds about $300 while, at the same time, filling the cab out completely.
One other thing you really should get and mess with before incinerating the Magic Plastic on this, and that would be to get a copy of VCV Rack. It's FREE...has software models of some of the hardware modules on MG, and works pretty much like yr.basic modular. Just remember: it wants a LOT of CPU power to really cut loose, but if you've got a computer made since the mid-2000s, you should be cool. https://vcvrack.com/
NB: for some reason, MG is only showing a link to the build on my end, not the actual build screenshot. Click on the link if you don't see the build in the post.