I'd like to see a mod that increases infantry range needs half again, or perhaps double. Pretty poor accuracy at the far end though. Either seriously decrease infantry running speed or up the stamina penalty. Possibly lower morale for both attackers and defenders in melee. Give artillery better range and sightly better accuracy across the board. Maybe lower the height of bouncing cannonballs, if possible. They always seem to bounce right over everything.
You may be interested in http://www.twcenter.net/forums/showthread.php?t=240571. I haven't personally given it a try, but seems to be what you are looking for.