There's a problem currently with how doors installation is tied to floor building, as people who buy upgraded doors on auction can't fit them into their houses if they have three floors, as well as not being able to switch doors between floors.
While I don't know anything about the behind-the-scenes coding etc of this problem, I'm assuming something will have to be done to un-link door installation and floor building.
So when this is done, I'm wondering if we would be able to get decoration-only doors? I'd love to have more doors in my house than what is allowed currently. For example, there is one door allowed on the first floor, which goes to the second floor. In addition to that door I'd love to be able to place a non-functional door on the first floor to create the illusion of more rooms.
And that way if I ever wanted to bring into my three floor house a door I bought on auction or switch doors between floors, I could use an intermediate door if necessary - first place it as decoration only, then switch the function to this new door, and so forth until I get the placement that I want.