I really enjoy the prompt in the Bandit Hideouts to fight 1v1 and wish there were more occasions in the game where you are offered a 1v1 fight.
Would be nice if somebody handled a mod where when you are defending a city and it gets attacked, and you parley with the attacking army's leader, you could request a 1v1 fight to determine the fate of the city.
Another option would be when you are "taken prisoner" after losing a fight. Instead of being helplessly dragged around, would be nice if you could request a 1v1 trial by combat. If you win you're released, if you lose, you die.