Agreed, you all have made some great points regarding LOS tool from places other that your unit.
However, it would be nice, using the same principal, to get a COT (circle of topography) if not directed from a selected unit. OK, you can scan over the map at the lowest detail to get "potential" LOS's. COT can only be used realistically of the higher views when your looking down. Using the standard map colour coordination (blue, green, brown yellow white, clever shading, mentioned before, etc), you could get a flavour of the hills. I know that there are no moutain ranges or great chasms in the battle maps, but it could be done, say a different color per metre.
I believe this is not an unrealistic feature, rather, its aids the camera, an allows the user to "see" depressions on the map enabling troops to navigate easier, rather than mousing along at the lowest level, looking all around, seeing if they can be spotted. If find that very time consuming.