I don't see any of these ideas working.

The roof is fine in height.
I can't add a dark sky with clouds that is close to the one used in the game without creating a custom skybox which I don't have the ability nor the desire to do.
Adding the four extra rooms will not enhance the gameplay because there is no reason to go into those rooms. The ones I created are barely used.
I can't widen Griffin's office without having to resize the entire map, which I'm really not in the mood to do at this point.
The lighting is fine. There is hardly a noticeable difference.