Well, problem #1 here seems to be that there's a lot of big footprints in a smaller-sized case. The Batumi addition is a better direction to go in, where you can have a lot of function in a much smaller hp count. As for this being "too heavy" on sources...hm...yes and no. Having plenty of VCOs is a good thing, however you make it fit. But having too many "showpiece" sources...not so much so. In this case, you've got three: the DPO, Cloud Terrarium, and Mysteron. The only "basic" VCO present is the STO...and this neglects the ability to have basic, boring, utilitarian VCOs as effective audio-frequency modulators, either as FM sources for other oscillators or as mixable audio sources to add to other oscillator signals with a bit of detuning and/or waveform difference to beef up basic sounds. This is something you might want to reconsider, perhaps losing the Mysteron in favor of a few very basic VCOs for those purposes.
Dynamix...no. You have a pair of proper vactrol LPGs in the Optomix already. What's needed are...yep...boring, dull, sleepy VCAs. Again, this goes toward sonic complexity. Dropping something like a Doepfer A-135-2 quad VCA into the Dynamix's space would then give you four DC-coupled linear VCAs which can then be used to process CVs, LFO and other modulation signals, as well as mixing these if desired. Yes, VCAs are boring. But they're also bread-and-butter devices when it comes to being able to create complex control paths.
Another glaring omission...and also boring stuff but necessary: mixers. I don't see any...and that's a crippling issue. You can't make really good use of all of those audio sources unless you also have the ability to mix some of them together. That last thing I suggest above, combining the STO output with some other source's...you actually don't have a good way to do that right now. Like VCAs, mixers are boring but 100% essential. You need ways to combine audio and CV/mod sources; the whole point of "synthesis" is to reach a sonic result by combining signals to create very complex and changing spectra. The DPO can do this...but that's the only thing here that can, and by leaving mixing out just for audio alone, you've hamstrung this build.
Some of your other module purchase ideas suggest the real problem, actually. There's always the temptation to go for the big-name, super-sexy modules...but if you do that, you're going to wind up totally screwed. Some of them are nice to have, but if you neglect the sleepy-looking parts like mixers, VCAs, envelope gens (only one in this...that's not going to cut it!) and on and on, you'll have a sexy-looking box that works like crap as a synth. Couple that with the space limits in your existing cab, and it doesn't surprise me at all that you've realized you're lacking flexibility. But to get that flexibility...big and sexy is not the answer. Spend some time looking at dull, boring things...consider how they might fit with your other modules, and which modules it might seem that can be removed in order to optimize the capabilties of the remaining ones. Those boring scut-worky modules are actually the key modules that make the pile of modules into a workable instrument...and without them, yep, you've got something expensive and lacking.