How about a backpack that you craft and it carries 3 of every tool, your bed, crafting table, and furnace, that way you dont have to waste inventory slots whenever youre underground mining, and can carry a larger load of bounty back with you. I love exploring caves, and mining but my inventory fills up so quickly and I have to head back to dump it.
Part of me likes this idea, because, I too, fill my inventory very quickly, and had almost suggested something of the effect... But, part of me thinks it would make it too efficient to mine and carry about even more obscene amounts of stuff (as if carrying around several thousand metric tonnes of dirt gravel, sand, and cobblestone in just your inventory alone isn't obscene already).
Backpack