I just have to say this.
I know this is a game and everything but the whole point of having an empire is that more often than not two armies facing each other were not equal, even in equipment terms. This happens quite often in the single player game, but it still doesn't mean that the smaller army would be destroyed. I take the battle of Agincort(!?!) as an example, outnumbered by about 2000 troups tired wet and wanting t go home Henry kicked ass and anhiliated the french army and only lost 400 men.
This is also a good time to complain about peoples attitudes to the 'defending' player in MP. Why would you leave a hilly position when you didn't have to? I know it doesn't make a really great, fun game but this is war, and people do die. Some great general chap said once: Terrain is worth an extra army.
Why squander it?
As a way around this you could go around the various maps and give the defending player a smaller amount of Koku if they are going to sit on a hill or you could have a new game type in that there is no defender, only attackers. This seems far more sensible to me than complaining that some people sit on the top of a hill and are difficult to shift, or should, the defending player come out of the hills to fight, comended for having a 'fair' fight.