I personally think this is a great conversation for this forum, thanks for starting the thread. Lately, I've also been thinking about body positioning while riding my bicycles. I have two bicycles that I use for multi-day touring- one is an old road touring rig, the other is an old mountain bike that I've set up for touring routes with significant off-road stretches. While touring on either bicycle, my cockpit setup has been similar- drop bars with the tops level with the saddle height and a reasonable stem length. But recently I've also started to play around with upright body positioning and swept back handlebars on my around-town commuter bike, and it's been a revelation. So I've been asking myself the same question- would I want to replicate this upright body position while on longer tours?
One part of me thinks not. I think that the slightly bent forward position with a drop bar is the best solution for me, as it allows me to balance/switch my weight between my hands, legs, and butt throughout a full day of riding while allowing for multiple hand/body positions, including one that allows me to hide from hellish headwinds. For me, swept-back bars and upright body positions are really great for short and medium rides, and I could definitely enjoy riding like that for overnighters or shorter touring days, but I think it'd really get to me after multiple long days in the saddle. Maybe if I had a good upright handlebar with multiple hand/body positions like a VO crazy bar, but probably not if I was riding a Rivendell-esque cockpit that realistically only has one or two solid hand/body positions.
The other part of me thinks sure, why not? Human bodies can be extremely adaptable and capable, and you just need to have the right attitude, realistic goals, and an appropriate pace.