L69 - wilddog and others are working on trying to make the walls etc moddable but it will be ages before anyone can do anything usable.
so we're stuck with cities with 1 wall and the central plaza.
I think it might be possible to move the central plaza though - as we've done that for the new castle / forts and the ambient building "forts".
could make for some interesting battles if we can open up those corner "castles" in the city battle maps and place the plaza in there.
need to possibly re-do the pathfinding, and I've no idea how the AI would cope with it.
(meantime the new SS6.3 has just started beta testing - let's just say it looks weird after playing the RozMod for a few months.)