If your dead set against a bumper mount try fabricating a bedcap style plate running from top to bottom, allowing clearance for the gate to open.
you might want to run a plate out at a 90 degree angle to the face of the gate, to help support the weight of the tire & wheel, along with what ever you use to hold the tire to the gate. Make sure the lower support is high enough to clear the bumper (if you have one) when the gate is down. I would probably consider running plate end to end, build a heavier hinge & latch set up, with safety cables, just in case. Like they said it's only sheet metal. Thats alot of extra weight for the hardware to support. It would probably be easier & lighter to fabricate one from scratch. As for access to the handle, Ferrari used rope on their windows. It seem a lot more at home in a K5. Rope lift for tailgate glass, or side glass seems a pretty easy fix for a regulator you can't afford.