Pros and cons for the tower discussion :
-cons :
I think it's against the kam style, because the military units are completely different of the citizens, how would the archers/crossbowmen be fed ? Should they go to the inn (a military unit ? no !) or be fed like normal military units ? (strange too).
It's already hard to kill towers, but with an archer/crossbowman with increased range on top of it ? Let's imagine, you would have to kill towers with a looot of archers, and most of them will die because of the great range of the tower. Being able to kill the archers on top of the tower while the tower is still alive would be ridiculous too, let's see how you want to balance that

-pros :
But ! It'd be quite realistic too. (more than recruits throwing rocks :p)
Maybe the use of a new citizen unit, the "town defender", that'd be totally strange too.
-> As it is now, I think it's a bad idea.