Is there a mod that removes the ladders you have immediately access to in seiges?

I think the original Rome TW's system of not being able to seige city with walls from turn one was much better, because it allows for the defender time to send an army and lift the siege. Without it, you cannot defend say 3 nearby cities with one army as you have to guess where the enemy will attack and he can always go for the other ones.

This shouldn't be that hard to mod, right?