Hello guys and gals,
I’m a bit stuck. Do I really need VCAs?
Do I need effects?
Do I need a mixer?
What would you do to finish off this rack?
Help would be very, very helpful.
Thanks.
-- clivevass

You may wanna ask yourself what's the purpose of your system. Show that rack to 10 different people and ask them what module they'd buy next. You'll get 10 different answers, all of which would take those people one step further towards their dream rack but may be completely irrelevant for your musical approach. Are there any modular synth artists or youtubers you really dig? Anything you'd like your system to do which it can't quite do yet? The answer to all of your questions is "no, you don't need that", if you're able to get all the results from your system you could wish for. Then all that's left to be added are some blank panels to cover up the holes.
As for my personal opinion and what I would add to the rack, I agree with JimHowell. Utilities are king. Switches, mixers, logic, attenuators/attenuverters.. Happy Nerding's 3x MIA covers a lot of these functions at only 6HP and it's really affordable, too. In fact I love all of Happy Nerding's utilities.
I'd definitely add a cascading/mixing quad VCA. Mutable's Veils appears on the used market now and then. Other great and inexpensive options are Intellijel's Quad VCA or ALM's Tangle Quartet. The latter one doesn't exactly have that cascading behaviour but has a mix output. Only linear response, too, other than Veils and Quad VCA.
I'd personally add another VCF, maybe a versatile dual one (Intellijel Morgasmatron, DinSync Sara, AJH Gemini, which is rather huge though), delay/echo/reverb like Mimeophon, some sort of end-of-chain mixer in order to blend wet and dry signals. Oh, and function generators (Shakmat Triple Steeple, Intellijel Quadrax, Joranalogue Contour 1, Cosmotronic Delta V). A designated CV mixer, too. I'd also have Assimil8or swap places with Tetrapad/Tête, just for the aesthetic of having them sit next to Metropolix (and because their inputs and outputs are located at the modules' top anyway which is great for bottom row modules).