here are some pics
When the door is open (motion detected), the stepper motor pulls the rope back till it "homes" against the metal plate. When the door is closed, the stepper moves 90* and the slack in the rope allows the door to close.
i don't want to out anything on the outside of the door.
I'm not 100 percent sure, but just from reading a little bit after posting this question, i doubt my current set up will be practical because i am going to need an extremely large amount of force to move the lever because the arc-moment is essentially zero.
i might try to attach the rope to nuts on a leadscrew and take advantage of the ole incline plane.