Great thread, lots of info. I'll add just a note from my perspective. If you go F450/F550 or Ram 4500/5500, the main advantage is the TURNING RADIUS that wide front axle gives you. This is not a trivial advantage. Go drive one and you will see. Flipping around on remote forest roads or in tight canyons is hard. 2nd advantage is the tougher running gear, and at camper weights, and you want it. Fact is you may end up be de-rating the springs or mitigating it somehow (Kelderman, spring packs, Sulastic spring etc) especially if you remove the camper at all to do truck stuff, whereas with a 1 ton you will be accentuating it (airbags, helper springs) so that's a wash. A drawback is if you want to avoid dual rears, you have to do super singles at a cost of $6k minimum. Then you are tied to huge tires like MPT81 or you lose payload with 37 inch Mickey Thompsons etc. You also have longer bed lengths available with 84"c/a. But that kills breakover and gives you a longer truck. Alas, it's all compromises.
If going flat-deck, the primary advantage of a tapered rear on your camper has nothing to do with departure angle, it's simply to squeeze a larger floorplan from a smaller footprint. Ei you can have a 10 foot camper on a 8 foot bed. Departure angle is limited by your bumper/hitch and any other below deck stuff. I've yet to see a duck ass camper whose departure angle advantage isn't completely defeated other stuff below the deck. Also note your read camper jack points have to be higher with those designs. I think flatbed designs are the way to go, but remember there are ZERO off the shelf campers available in flat-deck config, so custom or self built, and the attendant 1 to 4 year build lead or build process, rears its head. Just some food for thought.
So my plan is thus: get an interim "imperfect" camper for my flatbed that I can use for a year or two while my custom camper is being fleshed out. Shouldn't lose too much cash when I sell it AND I get to go camping THIS YEAR. Well that's the theory anyway.