How about creating only 1 point on the map where you can retreat through (high velocity space current?). This way it makes running away a bit more challenging then just heading for any edge on the playing grid, and it gives one of the combatants the strategy of trying to block the escape route from the other attacker/defender.
The escape route could be placed in the same place on every map or could be placed randomly for added difficulty.
Has this been suggested before? Probably, but i'm too lazy to check
