the AI does not have to be a militant one in order to be difficult. If they are so far advanced over you, one of their tanks could clean house on your brigade of pikemen
i, too, want a hard AI, but it needs to have its balance - like civ II: the zulus/russians/etc. were militant and kept you ocuppied on that front, while the egyptians/etc. were tech advances on the other hand. i thought it was well balanced, but i just wish that the personalities are random (i.e. i dont want to see green or white and KNOW that they are militant, or that yellow is always a technocratic(?) nation)