Then you'd want a hip/back structures to help alleviate load which also helps with lugging around more batteries.

This seems like more of an edge case to me. You still have to hold the weight with your arms (even if assisted) and balance your center of mass. There is only a narrow range between where an able person doesn't really need the help and where the pallet jack/fork lift is a better solution. This is especially true when you consider what happens if you drop the item in question. There are certainly cases where a solution like this is perfect, but I think they'll be rather niche.