Would it be possible to implement another wallpart or modification to an existing wall, called a sally? A sally is a small one man gate in a castle wall. Its simply a small hole with an hardwood door reinforced with ironbands or a small iron door.
We thought about this, because we wanted to make our castle defensable but usable, and we don´t wanted to build a gatehouse everywhere. For example we have a small yard, with apple trees in it, and walls around, its in our second defenseline. There are simply apple trees and a few archereytargets, looks nice, but we don´t need a full scale gate house to enter this yard, a simple small door (sally) would do the job. And yes there are other things you could do with a sally. Make a sortie and so on.