I got a crap load of ideas in my head for maps, im sure you do too... But I think youre going to one of the people that open a whole new world for us map makers. And now that I got rid of my dungeon on my first castle you are going to be the only one with any part of a castle underground. Check out the interior prison stuff (not dungeon) i think they would work pretty good for non prison looking interiors. Especially the piece that tall with one way in being stairs up to it. Its tall enough to put the flag in. I experimented with it for my map but opted not to use because my map is actually about having a city and trying to get the D out of the castle though right now they seem to huddle around the flag...
BTW im totally using the 360 degree spawn for attackers for an island siege im working out. It should be epic... Thank u for the new idea