OK...I did a bit to set up the general areas you'd want the various modules in. Note that my typical layouts put the audio sources and modifiers up top, modulation across the center, and mixing and effects in the bottom along with control systems. This allows for an "up on left, down on right" signal flow which makes the build much easier to patch and control.
You'll notice how the existing modules break up into the overall scheme. Also, if you don't already have that MIDI interface, you'll likely have a lot of trouble finding one as Doepfer discontinued it.
Now, one issue I do have is with the cab size. Those 84 hp rows are kinda tight, so it makes choosing just the right modules more important...and one way to choose is by function density. For example: there's a very basic Doepfer ADSR that fits into 8 hp. But if you put in one of their A-140-2 modules instead, you then get TWO envelope generators that work the same way (actually, the A-140-2 EGs also give you CV over time, which the A-140 doesn't have) in the same space. Note that there is a point where you can go too far with this; when you've gotten to a point that it's difficult to play the synth because the controls are all too tightly bunched, that's what "too far" looks like. But if you keep the density to somewhere within reason, you can majorly increase the build's capabilities without the need to go to a bigger cab, AND you'd still get more capabilities.