We're already pulling a really long fifth wheel at 42' 10" (supposedly), so I really don't want to add onto the back. That was a really interesting thought, though.
Gardening at home is pretty well out. We are hoping to be gone for about 6-8 weeks and the wildlife in the backyard is pretty abundant (for a suburban area!) - we regularly have deer, raccoon, rabbits and groundhogs in the backyard. (A full lot size that is only about 1/4 of an acre!)
I've been reading up on onions- it seems like they may be a lost cause, as well as they're a cold weather plant, too. But, we did use a relatively flat tray for our lettuce back when we tried it. I'm not sure what turned it bitter, though.
Protecting stuff in the truck bed is a trick as we pull a fifth wheel. At most, I can cover about 1/2 of the bed, but it's still open. I'd rather fashion some kind of protective "lids" for whatever planting pots that I come up with.
The weight of the pots with soil is another worry - simply from lifting them into and out of the truck bed. I'm really lazy.
The wilting is a worry, definitely. Especially if I'm covering them to protect them from the wind- seems like I'd be compounding the heat issue.