and linked
some suggestions:
let's start with mixing:
it doesn't look to me as though you are intending to use an external mixer - as you have the doepfer output module... but there's no end of chain mixer and no mono to stereo conversion - you have a mix of mono and stereo sound sources/sound modifiers - get something big enough that you can mix all your (processed) sound sources and place them in the stereo field - that means panning - you may want cv control over this - you may find that this means multiple modules - there are very few mixers that have mono and stereo inputs with cv-able panning on the mono inputs and send/return functionality - but you might find that a large mixer solves a lot of problems... hexmix & expander & hexvca or wmd performance mixer or tesseract tex-mix might be worth looking at - these mixers will satisfy most of the criteria above (to a greater or lesser extent) including the send/return which is really handy for the fx aid - you might want another 1 or 2 of these - delay/reverb/lofi - or something similar... and quite importantly, they have stereo master outputs and headphone sockets - so you can dump the doepfer module...
& there's not a lot of sub-mixing... so no mixing the 2 vcos in the 258t before hitting a filter for example...
the liivatera mixer is very large and would probably be better replaced with multiple smaller mixers - for example a couple of 3*MIA - remember that you will want to mix both audio and cv
there's a lot of gate to trigger channels, which you probably don't need - maybe keep the g&t - dump the ladik...
lfos: i'd dump the ochd and the eowave and replace with a batumi
vcas: I'd want more - dump both and get a couple of veils... again - you will want to vca both audio and cv
filters: ok 3 is about right - you might find you want a 4th dual/stereo one down the line
sequencing: I'd consideer swapping both the hermod and the md out for an erica black sequencer - 4 channels of up to 64 steps, with gate/quantized cv/modulation and mutes (better to mute the cv than the audio!!) for each and you can plug in a midi keyboard to record sequences - and the interface is much more ergonomic than the md - which if you wanted to use it for generating 'notes', you would also need a quantizer - maybe a 4 channel one... and/or possibly a sequential switch...
other modules: you might find you want a waveshaper - really useful with the 258t, an lpg and some more utilities: a sequential switch, a matrix mixer, some logic... take a look at my signature to find a rough guide to how to get the most versatile modular synth for the least money...
so I think it might be a good idea to add an extra row and I'd probably go for 104hp instead of 84hp - it looks like this is a DIY case so an extra row is relatively inexpensive - remember you do not need to fill it all at once - it's better to go slowly - but I think you will want more space to expand into in the future - based on the row power rack warts there's plenty of power - make sure you buy proper bus boards, to avoid rf issues with flying ones...
oh and Maths - keep Maths - it's a great module - even better if you work your way through the 'maths illustrated supplement' a few times and spend some time working out why it's doing what it's doing
"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