I feel the hexes are overly cluttered already
This is irrelevant.
I need a tool to see the all the invadable hex at the same time. I hate to have to scroll all over a map reading text. It is useful, but not enough. When I look at such thing, I don't need to see clearly the other things in the hexes. So the graphics can be invasive (like blue strip on the hex over everything else in the hex). It might not fit your taste but it fits my way of processing information to make decision.
I will try to make a graphic example tomorrow.
Though I am happy that one of my other idea seem to have reach you [;)] I need to earn my name on the "thank you" list. And it is really a good way to scroll the map (when not holding any unit in the cursor).










