can't agree more with what @HGSynth is saying above...
I'm not convinced more modulation is needed, in fact I'd probably go with less - and add more utilities to leverage the modulation that's there to produce more (& more interesting) modulation...
so more mixers (& usually I'd say more vcas - but I think you have more than enough) especially and End Of Chain Mixer (or more sub mixers) & at least 1 matrix mixer (predominantly for modulation purposes) would be useful...
more things like switches, attenuverters, clock dividers etc & even some mults... & yes I know pams can do a lot of clock division - but an external one is also useful... for example send an audio signal into a clock divider - /2 = -1ve, /4 = -2ve squarewave outputs (bassline)
also some control modules would be a good idea - so you can make big overall changes easily - but at that point an extra case might be useful - so you can have one vertical and one horizontal... this would also make room for a decent sequencer (I like the erica black) & EOC mixer...
one of those analogies @HGSynth mentioned above is my signature... take a look at it and spend some time thinking about it and how it applies to your rack... especially the formula!
hope this helps...
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities