I don't think it would be too hard to indicate bunkers and watchtowers in a legend next to the map.
e.g.
"This map has watchtowers. They are indicate by the graphic [which looks like this]. From a watchtower, you can see all the territories in the bonus."
Much like how the Jerusalem map has a legend which describes the cities visually.
https://www.warlight.net/Map/9359-Fall-Jerusalem-CrusadesOf course, it would be up to the individual map designers to use this feature in clever ways, and to make it clear. But that's already the case with all Warlight maps - anyone could, in theory, include weird and bizarre connections on a map without making them clear. (As happens sometimes by accident, when a mapmaker includes extra connections by accident, or missed a few.)
Edited 7/19/2015 16:53:25