Yes, and the door opens and the tire vibrates going down the road. The bumper is connected to the frame, the tire the body. They move a little differently so I think your idea of connecting them is challenging to make work during an impact.I do not believe it is difficult to conceptualize my idea. I believe anybody taking a look at how the spare tire is mounted on the rear door of Wrangler JL will notice the gap between the bottom of the tire and top of the bumper . I am not really too worried about it but I just thought to myself that placing and positioning of the spare tire could have been improved so that the tire in case of rear end accident would transfer the force of the impact into the bumper itself and not the door. I as well can see why the gap is needed for accommodating larger spare wheel.
Can you draw your idea as maybe myself and others are visualizing it differently than you.