agree about the debris. could have a rubber seal that wipes the tailgate as it retracts in, although it would most likely miss some and jam anyway.
the tailgate has so many uses. i do like the idea of left and right side rear bumper retractable steps, like the side steps.
just the specs of the diagram is what gave me the idea. if it can have a retractable hinge that drops the gate down that far that space could
hold a gate. even though that is the spare location. lower the spare or even raise the bed a little higher than the bumper.
a 3" box in between the bed and spare would hold a gate without the wide top .
a big dent would affect it at the back of the bed , depending on the depth of the dent.
i like it..