I think you have a real challenge on your hands to fit information from the Inner Plane diagrams, Outer Plane diagrams, find what is known about Spelljammer and also deal with the transitive planes on a single diagram.



I suppose that if you pulled some of the sidsbar text off of the map, and moved it to an accompanying handout (or had this image on a website with mouseover pop-ups that included the sidebar stuff) you could create even more whitespace and then try to find a way to pull the various symbols closer together.



But you are going to need to keep some whitespace. If you go too far the other way, you are going to create so much clutter that people can't tell what is what.



One thing I would say is that, when I zoom in on various small areas of this, it seems to me to be the perfect level of detail, whitespace and layout, for that close up aspect. I bet you could chop this image up and shuffle sidebar text (so that it wasn't chopped in half) and create about half a dozen handouts from this one diagram.