Well my portable bench with 4 adjustable legs only weighs about 20#. Mine has a sling attached and can be carried like a rifle.
It could even be less weight with a few design changes and not affect the stability. We use packs also, and Eberlestock is the one I prefer.
Mostly they are just used to carry the large binnoculars we use with a tripod shoved into the scabbard or strapped on the pack.
A military type pack frame would work well for carrying a small bench also, and could even be redesigned to be the actuall bench.
Mind you now were not walking around all day. When we leave the vehicle we have a destination in mind, usually less than a half mile depending on the type vehicle and a particular location.
When we get there, we are there, maybe even all day. I say we because there is always at least 2, a shooter and a spotter, and most often more. We each have our own glasses, but we share a gun, which although not by first choice, might be wearing a bipod.
A very important thing when L/R hunting is follow up shots, quite often at a different spot than the first shot. What ever is best for "you" doing that as quickly as possible, is the best system to use.