Have you tried AoD II? AI has been improved, and you may find natives and europeans being significantly more aggressive.
Frankly, I also think military is a bit "one dimensional", units are limited and the lack of technological progress makes things even more predictable.
I wish there was a way to implement technological progression (eg railroads and factories). This could include buildings, as well as musket technological progression: arquebus, musket, flintlock musket, rifle musket...
Tactical units like grenadiers (with their true anti-infantry use), light infantry, heavy infantry, musketeers, light and heavy cavalary, light and heavy artillery.
But... nuff said. I am now talking for a different game. Dale has already done wonders to transform a bugged and out-of-date game to a little miracle!
AoD II is by far the best you can get now!