Shogun2 is nearly in a perfect form. The siege units in shogun 2 is Totally USELESS!!! I mean no matter is player or computer, no one is using it except in the tutorial the first time i played
My suggestion is
1) Fire Projecting Mangonels should add wheels it, allow mobility and attack different wall and gates. Also, add a few more ammo.
2) European cannon should be able to deploy more area (closer to center) because they are unmovable. And also increase ammo and maybe cheaper upkeeping cost.
Please make it perfect for this game.