I definitely talk about ergonomics on here, though. It seems to be the most-neglected aspect of system design, module design, and so on. And it's very important, because ergonomics goes hand in hand with successful instrument design. Ignore it, and you'll probably wind up with a nice and expensive closet-stuffer.
As far as modules go, the problems there are twofold: in some cases, there seems to be ZERO forethought that their hardware might be used in low-lighting situations. Like a live gig. So you get panels that look like refried ASS attached to modules that could benefit from a much better and more intelligible user interface. And the other issue, especially with the plethora of Mutable clones, is tiny knobs packed densely together. Now, I HAVE a modular system that uses these pretty much exclusively, that being a 180-space AE system...but the AE module designs are such that you've got loads of room to fit your fat fingers into when you want to tweak a patch. THAT works. But when you've got a pile of little controls, jammed in with the necessary jacks, and tiny writing on that...well, to me, this is sort of crappy. Yes, bringing certain modules back (Clouds, in particular) is a good thing, unless your remake is unplayable...then it's not. Seriously...you can't jam 18 hp worth of module guts into 8 hp without some sort of tradeoff...I get that...but that compromise probably shouldn't be in the UI.
As for systems, I follow a pattern that has "generators" on top, then filters on the right, and FX and output mixer below that (at least, in a 3-row cab). Then on the bottom, clocking and related processes, and above that on the left, modulation sources. Granted, I have to fudge that arrangement sometimes, but you can even manage much of it in something small like a Rackbrute. By doing this every time (or as close as possible), I'm hoping that the arrangements I come up with actually have a signal flow such as this for the user's ease:
LEFT = UP, RIGHT = DOWN. Control signals start on the bottom with sequencing, MIDI interfacing, soundcard I/O, etc, then go up on the left along with modules to work with them in that path. Generators (oscillators and their pals) on top, as they're less likely to be tweaked while playing. And filters + FX go above the final output mixer, sent down the right side from the top. Modulators, if left in the middle, can then branch out to anywhere in that circular flow with a minimum of cable-snarl. And putting the FX right near the final mixer makes them easier to add to the mix. So, even though there might be several "instruments" patched up on a single synth, you're able to follow what's going on with the patches more easily.