So admittedly, I've already built this and it's fairly solid for drones, i.e.; does what it says on the tin. When I feel like doing something more rythmic I have an MFB Urzwerg Pro, Electro-Harmonix 8 Step Program and a TT-303 hence the lack of any sequencers. For effects I already had a bunch of guitar pedals with plenty of pitch shifting options and rack mount FX so the ADDAC200PI though I realise the drawback of those is a lack of CV. The primary focus of the rack is indeed drone and dark ambient, but I'm also interested in industrial, IDM, acid house and breakcore.

Most of the modules I chose for this I did so because they could do things I couldn't find a cost-effective way to do outside of modular (hence the E350, Morpheus, Warps etc.). A few of the modules here do synergise well and I feel like I have most bases covered including even sampling in a limited sense, but there just seems to be a certain something missing and I don't know what it is; I've considered going for a third row but actually finding it harder to come to a decision on what is most needed.

Here are some modules I've considered:
Serge triple waveshaper
ADDAC 207 quad intuitive quantizer - seems like a logical option for times when I need drones to mesh with other stuff outside of the modular tuning-wise
Mutable Instruments Shelves - a friend of mine once blew my mind with a certain sound when he modulated the frequency of an EQ at a high rate, this would give me the ability to do that on two channels and I could just use it as a conventional EQ & filter alongside it. It'd also make the ALM EQ obsolete though, most likely.
Zvex Instant Lofi Junky - A chorus which you couldn't come across too easily outside of modular. Sure there's also a version of it in pedal format but that doesn't have the CV control!
Expert Sleepers FH-1/2 or Endorphin.es Shuttle Control - obviously for MIDI to CV/Gate control, I'm really on the fence about whether either of these would be useful for me. I have a MIDI I/O PCI card so it would mean I could control the modular with software, which is potentially a big deal?
Intellijel Shifty - looks like there are some useful utilities on offer here, I do sometimes find that I wish I had more than the one channel of S&H from the Pittsburgh Mod Tools.
Zlob modular VnIcursal - You know what they say about how you can never have enough VCAs, and I can't get enough of the idea of combined VCAs and mixers. This is like Intellijel quad VCA only even more space-efficient to me, and if I need the features of the quad VCA I'd be keeping that.
2hp LFO - between the Batumi, Kamieniec, Mod Tools etc. I have a few LFOs, but a couple more couldn't hurt and might come in handy when there's 3 rows to work with?
I was thinking in addition to this, maybe a compressor, since modulating the E350 tends to cause volume spikes in certain waveforms, but I'm not sure how effective that would be?
Something else that might be useful is a slewer? On the other hand, I can't say I've ever felt a real need for one.

Would like to know what your thoughts are on these ideas for a third row. Feel free to roast me over the decisions on the two rows I've already got!

Oh and just a patch I loved on the IDM/breakcore side of things that might be worth trying for any of you: I have the Warps on the obligatory Parasite firmware, patched a Korg ES-1 into the ADDAC200PI then through the Warps on Comparator, then back out. Results in extremely aggressive sounding drums!

Edit: And some more modules I have considered:
Befaco Rampage
NerdSeq - It would be nice to be able to play this portably if I don't use a FH-1/2 or Shuttle Control. my primary DAW software is a tracker so the interface is familiar to me and it has enough channels.

I'm open to ideas of different modules than the ones I've mentioned and prepared to accept I may have some ideas which don't make sense here. I haven't felt like there's a particular module I've got that was a mistake (though I don't find I use the Dreadbox WL Divider much) but if there's any I should really get rid of I could accept that too.