Not all that familiar with car design, but on aircraft, something similar would be mostly for torsional rigidity.
For example on many aircraft the rear baggage bulkhead is very light weight aluminum and weak looking, but it is necessary for torsional structure.
I would thing that the same premise would apply to the Camaro.
Hmm all this fancy talk make me think it might not be such a good idea. Still think it would be really cool. Maybe I have to look into reinforcing it super close to the window so I can have still have the extra storage.