Modding walls questions.

#1:

Is it possible to mod in "interruptions" in the ramparts of a city. In other words, when a unit climbs to the ramparts by ladders , I don't want it to be able to run around the entire circuit of the city wall and capture all the towers. I want to make an obstacle every 2 towers to force me to climb down into the city. Is that doable?

#2: Is it possible to mod the city wall towers to only fire when held by the defense, and not fire at all when captured by the attackers. (instead of turning against the defenders).

Thanks