Some module suggestions:
-- Erogenous Tones units would be my top suggestions as you could add a LOT of envelopes, simple LFOs, VCAs, attenuverters etc with a few modules, e.g., get a lot of "power up" to your rig with little HP by using these very "dense" modules. I consider something like 4ms SISM or ET Levit8 critical in a medium to large system; I need at least 1 SISM if not more in a big build. ET VC8 would be a very HP efficient way to add VCAs if you're needing more.
-- Instruo Ochd, I see you already have, but honestly you could stand even more LFOs in a rig this size? Ochd is a great choice, I have multiples. I love Mutable Instruments Tides, but that is rather different from Ochd. If you're going to get ET Radar, those 8 lanes can be used as simple LFOs or as envelopes
-- WMD performance mixer, as others have said, just makes a ton of sense with a system this big
-- the Random and Chaos type units from NonLinear Circuits are IMO very interesting and on my list of "next" modules
-- if you wanted to add further sources and filters, the Rossum stuff is great. Their filters have really changed my mind what a filter is.
-- looking at your build and comments, I'm seeing a ton from Erica (Techno, Fusion, Black systems), MN Black and Gold, and a major portion of the Instruo lineup. Can you share with us a little i) how you got to your existing system ii) some of your goals / vision for your system as it evolves? That would help us give a bit more tailored input
-- if I had the units you do, I would probably focus next on adding a significant number of "boring" modules, utilities and such, to "superpower" the modules already possessed. IMO the "boring" modules are hardest to understand initially, but go a very long way to add depth and playability to a modular system. My early systems were overly skewed towards sound sources; as a result, the system seemed "flat" (e.g. lacking real depth, power, complexity). It was adding a big complement of "supporting lineup" modules that really balanced my rig and gave it a lot of depth and interest. I think this rig could get a great lift from an added complement of utilities. To that end, practically, I'd suggest you scan through the more "humble" looking offerings from Doepfer and Ladik; for not a lot of $s or HP you could really add a ton of function and depth to your rig. The options from Deopfer and Ladik are too numerous to list, and particular selections really depend on what direction you'd like to take your rig.
-- what are the semimodular items you mentioned using for a lot of modulation etc? It's kind of hard to get a real sense of your setup without knowing the significant external items you link to the modular to fulfill some needed modular functions. Maybe you don't need some of the items I'm suggesting because they're already represented in your semi-modular?
Hope this helps some! Cheers, Nicholas