I made this observation over on the A2 forum:
I think 2 people could play this through the editor. It would mean new editor functionality though, either that or a specific editor-lite especially for this game mode.2 opposing players, each opens the editor. One player places defences around a selected area on the map, the other organises an offensive force to occupy that same area. Neither knows the plans of the other.
Then, the missions are merged into one using the merge missions editor functionality. Neither player must observe the newly merged mission, they just play blind.
Obviously, some sort of agreement must exist between the players as to unit numbers and vehicle counts etc.