Its a novel idea but I do see a couple of issues. Nothing that cant be worked around.
Unless you double-hinge it to open either way, it might end up angled the wrong way in some parking scenarios especially in the winter with low sun angles.
And during sunlight hours, the bottom of a panel can get pretty warm, acting like a heater panel into the interior. And you shouldn't insulate the bottom of one, so that also compromises thermal efficiency of your vehicle on cold winter nights.
But you could velcro a piece of foam onto the underside during cold winter nights, and then remove it during the warmer days.
The dimensions of a 100 watt panel mean that you would probably have to cut several roof spars, weakening the metal roof, unless you left them in place. A fiberglass high-top could be made and framed to accomodate that size cut-out. A 50 watt rigid panel might work out better, as far as the size of the opening.
Thinking outside the box, I like it...overall, I think it is a 'cool' idea!
