In some maps, where map creators implement castles, fortifications, trenches and similar obstacles, current game mechanics doesn't allow easy defense of such points. Making choke points on particular positions is helpful, but doesn't solve all the problems the players can meet in game plays.
If we, for example, take a single fort in consideration (one territory big) - it is easy to implement in this game as from there is possible to check surrounding territories by implementing enough armies in it, and, if such position gives income, it can generate probably enough income to sustain defense for several turns. In LD games such position should generate income to be self sustain.
However, if the map creator designed castle, citadel or some fortified city, there are obvious entrances via main gates, but, map creator can't leave connection between walls and outer lands if he want that castle have some choke points to provide security to units inside of castle not to be attacked via walls (and vice versa).
My proposal for game mechanic is to allow map creators to design territory connections between to adjacent (or distant) cells doing either (or both):
1. One cell (wall, tower, etc.) can see what is going on in adjacent cells outside of castle, while not providing information about own size.
2. The same cell can see what is going on in adjacent cell(s) outside of the castle and can do ordinary attack on adjacent cell while attack in opposite direction is not possible. In this case, adjacent cell should be able to see size of the unit on that wall (so he can prepare defense there).
This was some significant points on the map become more important as they can provide some players more time, if they are under siege, to help relieving units to come in time for help.
This proposal can greatly influence team games (with 2 or more teams on larger maps), diplomacy games, but don't think it should be implemented in competition games such as ladders, tournaments, etc. save if they are designed around such maps for purpose of extending game play.