Thanks for the input Yeah, of course, true…
I'm going to need to discard the plot plan for time reasons though :/ Will focus on labeling instead, which feels more important.
Here's som progress (again just a section I'm afraid, will scan the whole thing when I have more time!). Played around a bit with textures, aiming for something more abstract than usually...
Click image for larger version. 

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(And the colors turned out totally different to the last scan… another thing I will correct soon… maybe Tuesday.)