Glenn - just to point out what you are discovering but creating editor map overlays can be a major task in itself. I find a blend of period maps (1:25k ideally) period photos if they can be found and GE provide the most help. The period map will give an indication of the built up areas at time, road nets etc and contours, while GE allows a level of detail re individual houses etc if the location has not change too much since WW2 or what ever period. A great many places, particularly rural areas in Europe have not changed a great deal since the war, but other areas are almost unrecognisable.
Just for fun, but below are the overlays I used when I created the Arnhem Road Bridge map. It's worth noting that the bridge is not even showing on the period maps having only just been completed at that time, and so 1st AB were working with maps that did not include the bridge !!