With the siege update that is comming, I think that some defensive options should be enhanced, I mean the units on the walls and the trebuchets upgrade have the same range as land units, I think that despite being unlogical, it's also unbalanced, in fact there were several times in a lot of castle map were the enemies trebuchets or archers can attacks the walls and stationned units without any risks of beeing attacked by the defences of the castle, the walls despite the defence they give to the defender avoiding ennemies to enter into the city also allow the defensive archers to fire their arrows in a longer range than they could on a landscape, I think that the walls should give a bonus to the units giving them longer range and that the trebuchets should have a bigger range too...