In Delirious New York, Rem Koolhaas talks about the relation between form and function. He is interested how function could vary depending on the situation without changing the form. This is seen in the elevator.
The elevator is not simply just a mode of transportation of the disabled father, but instead it creates a space for everyone.
Ground Floor
The absence of the elevator would block any path to the wine cellar and thus the elevator would functions as a passage for the wine cellar. Furthermore, by having the elevator in the ground floor, it allow light from the first floor, go inside the cave-like ground floor.
First Floor
The absence of the elevator would create a void thus separate the floor, especially with the bookcase and structural beam that cuts through the floor. Thus, the second floor would have varies of 'space' such as a studio, gallery space, etc. But with the addition of the elevator, the floor becomes an extension of the floor and combine the room into one large space. When the elevator are turned into an office space, and the office space would then extends toward the
Top Floor
With elevator, the top level would have an office next to the bedroom, but without the elevator, the room could functions as a bedroom. The void left by the elevator would also create air ventilation.