I'd be interested in a Build System that allowed you to change the style and and Movements of a Door or Window, Like replacing the Glass with Rice Paper, or changing a Door into a Sliding door, these would be awsome features if Implemented, especally for builders, and perhaps a similer function for Stairs as well, Like Having Spiral Stairs that work off of the Stairs already ingame (as in the Theme of stairs, like the Ascension Staircase, or otherwise).