Originally Posted by
reppans
Full backpacks on rear racks seem pretty popular among the Brompton tourers -
THIS couple were half way through an around-the-world trip. I imagine such a load would feel pretty nasty for stand-up climbing, but seated riding shouldn't be so bad. On account of the small wheels, the CoG shouldn't be so far off a traditional rig.

I would think that is quite unstable and would sway. Perhaps if you can figure out how to lash it to the back of the saddle to control side to side swaying? I am an engineer, so I think about things like that when I see a setup like that.
My foldup bike uses 24 inch wheels, so it is much closer to being a normal type of bike. I have not toured on it, but I have considered touring on it. But I was leaning towards racks and panniers and a Nelson Long Flap saddlebag.
You mentioned standup climbing. I have not had any cycling related knee issues for over a decade now after I quit standing on the pedals to accelerate or power up a hill. I stay in the saddle and have much happier knees.