Ive been thinking about a canopy as well for camping. I keep thinking a high rise with a camper vent to make it a bit more usable inside. I think it would work good for snowy days too as it would put a bit of extra weight on the back wheels for traction
I liked having a canopy on the back for camping. My old truck had an aluminum one on it I thought was great at first. Aluminum was nice and light. I could install or remove it myself. It had 2 glass windows in the center of both sides. They were crank windows and had a screen to make sure mosquitoes didn't get me. Between the top of the bed rails and the bottom of the canopy I used weather stripping to make sure it was waterproof. I secured it to the truck with 6 canopy clamps.... but when I started doing a lot of off roading with it I had problems. The frame allows the truck to twist so much I ended up blowing out BOTH glass side windows. The dark dome tinted ones were plastic and would buckle and pop but didn't break. The aluminum on the top would ripple and pop also, and I eneded up breaking sone of the aluminum supports on the inside. To replace the side glass I ended up using epoxy and gluing in some plexiglass. This didn't break.
I'm not sure how a more expensive fiberglass one would hold up. For one it would be too heavy to remove without some sort of hoist/winch setup with one person. And how strong are they? I don't know. Chevy Blazer ones are fine, but they do have some steel re-inforcement in them I believe.
On my current truck I bought a canvas top. It can be taken down in minutes, it flexes without problem, and it is waterproof.
I've built the truck to make sure I can still get around in case of an emergency. A few years ago I lived on the side of the mountain with 1 official road out. Forest fires are a big problem in the summer and I had always been prepared if the bottom of the mountain caught fire, how would I get out? There was a trail to go straight up and over the mountain and then meet up with a forest service road on the backside. Not easy, but possible.
Also can have some bad blizzards up here which had made roads almost impassible. I have seen the county plows off in the ditch stuck and drove on by them (after asking if they were ok). It does pay off to have a good "emergency vehicle" just in case.