You know I actually rather liked the gaming board concepts of the original MTW or shogun, where the defender always has the option of fighting a field battle before hiding in their fortress. I would love to see that option returned, ideally with the defender chosing the ground for the fight.

Also, if the game's concepts were to change and develop, I would like to see some kind of cultural border control /influence along the lines of how its done in Civ 4.

Temporary forts, the defender should be given the option to leave before the seige, ie without getting stuck with the choice of having to sally or starve!

Lastly, would want the bigger rivers to be more of an obstacle and various tactical options for crossing them made available, possibly in the same sort of format as a seige