The rear quarter panels are structural. Not happening unless the car has a well built cage designed for the removal of the quarter panels.
I don't see how carbon braces would do anything. These parts are not autoclaved prepreg carbon. The cost alone to engineer a useful brace and make it out of prepreg carbon would far exceed the cost of even the nicest miata on this forum.
I really like that GV rear bumper, but it is still available. Hate supporting the idea of knockoffs of available parts.
I always liked the NB version of that bumper much better. The NA version just looks like a stock cut in half bumper.