I want to suggest portable version of backpack, so you can just fold your empty backpack and place it into inventory.
It would be really nice if we can carry our empty backpacks with us and use them when we need them. It can be special backpack which you can loot from bosses, or it can be backpack bag, which can hold any empty backpack
I don't mind if i have to kill 50 Misery toadstools as Wes with bug net for this item, but it can make people use more body slot items
Backpack is obviously most popular item now, and additional equip slot is one of the most popular mods too, because people don't want to drop their backpacks, but want to use other body items too.
Maybe making it epic boss loot can make people to drop mods and increase body items popularity