Sends clowns.
I dont see how you could redesign the graph to make it easier to read. As i recall, the graphs take into account the fact that the legal requirements state that you need to take 50% of the head wind and 150% of a tail wind when doing performance calculations, thus the contour lines will have very different gradients....which they do. Now if we put the reference line at the start, both the tail and headwind components would be above the reference line going in different directions. This , in my opinion, would clutter the graph even more. Thus making the already questionable print quality of the manuals that you receive in the exams, even harder to use when under exam stress.
Do you know the person who put the manuals together? I heard he received approximately £60k for his efforts. To me it looks like all he did was photocopy the boieng manual. Not a bad job if you can get it!