With proper order of placement, everything seen can be done without GM commands (interior walls are the hardest!) Everything else is a matter of moving the movable objects carefully, especially in the case of the area within the interior walls, which requires exact locations to not collapse and to still fit given the latest updates! Still, you can effectively build a floor and place furniture on top!
And a top floor, with access to all areas and furniture!
Now, who wants to come over and hang with some food and drinks?