I agree. Better uses of diplomacy and spies would make MTW even better. I don't think there is much that can be done to improve the battlefield element, but the campaign map could benefit from some tweaks.

Being able to plant spies on an enemy faction leader and getting them to convince him to attack another faction. Perhaps an ally, who has lands you want but can't legitmately attack, so you need to cancel the alliance by getting the ally to make war on another ally, then allying with the attacked faction if you get my meaning...

Also, I want a new strategic agent. One who can spy better than a spy, assassinate better than an assassin, and form stronger alliances than a princess marrying. Yes. a court jester.