Looking at the specs for a new F150 XL base model with the 3.3L V6 regular cab. The max payload (brochure) is 1990lbs for 6' bed and 1960lbs for 8' bed. In 4x4 it's 1730lbs and 1920lbs respectively.
A FWC Shell model as I've optioned it weighs (website) 951lbs for Hawk 6' bed and 1041lbs for Grandby 8' bed. This, on paper, means that my dry weights are approx 50-60% of max payload. factor in two avg adults plus gear and provisions and I shouls still be under the brochure payload.
I've read as much as I can find on FWCs and F150s and I know there are bigger more expensive engines and upgrades most people want. The theoretical question here is: will the base model F150 XL regular cab + FWC Shell work or will it suck?
The short bed regular cab appeals to me and the camper would be on full time. Travels are mostly Western US and Canada. The long bed is probably too big for my in town use but the extra camper sounds nice.