And that's why the four backpacks need to get lost! Add baseline "pockets", steal non-storage hotbar idea from Factorio to compensate, add belt pouch slot and a back slot, categorize items into two sizes: small and large.
Small items can be placed in any inventory, large items can only be carried in the back slot, either a single stack directly, or however many fit into a carryable container.
Boom, a much more immersive inventory system without the annoyance of having both the slot and the weight limit, or having to come up with weight ratings for everything.