• The ability to put (3d modeled) mechanisms on door factory doors, with the choice between a lever
  or a fire escape-esque pushbar.

• An option to place hatches horizontally, similar to the giant Abandonment Hatch at the start of Portal 2's
  Chapter 5

• Keys! These can be used to place (also 3d modeled), configurable locks on door factory doors. Shift-
  right click to configure, such as destroying the key, requiring multiple keys and a lock style (high-
  tech, traditional door lock or a scanner). Numerous types of keys, including keycards, would exist and
  the same type must be used to interact with the lock. Intended, obviously, for adventure maps and
  security.

• To help with 2, add COLOSSAL hatches.

• Place signs over rotating/vanilla doors to 'board them up' and leave them unusable until the signs
  are broken.

• A doorstop to fulfill a similar purpose whilst being less intrusive.

• A new, futuristic-style open/close animation. The door would move forward a bit, split
  horizontally and then rotate slightly, giving a convex (bulge out) or concave (bulge in) shape.

• Oh yeah, and if key(cards) were not to player's liking, biometrics could be attached and configured
  with a white/blacklist.

• A 3x3 Spiral Piston Door-esque animation.

• A creative-exclusive lockpick.

Another suggestion I have is to have single 3x3 doors, not just the double ones. They're cool but we would also like to have only one door in our house front instead of two.