Inventory

What if you could put on your back a Porter’s Frame (A sturdy wooden carrying frame you can carry on your back (in real life it is used to transport supplies to places where there are no road access)). The frame would acts like a bundle for only 1 item, it would accept the following items and places it in the frame (they are displayed on the player's back):
1. Chest - Adds 3 rows of inventory space but will spill out the content if chest removed out the frame. And allows transport of shulker boxes in these slots.
2. Crafting table - Allows player to access a 3x3 crafting grid from inventory.
3. Furnace - Allows players to smelt things basically from their inventory. Gimmick: Sitting in a minecart while furnace is active will boost the minecart.
4. Shulker box - Extends the inventory by 3 rows and is easily swapable with other shulker boxes.
5. Ender chest - Allows player to access their ender chest without having to place an ender chest.
6+. Stone cutter, cartography table, smithing table, loom and other crafting stations.
In a way this should grant the player a switchable inventory, actively more than doubling the player's inventory.

As for how to obtain this.... I think it can be early game, if it takes the chestplate slot, it will not allow elytra to be equipped at the same time which in turn balances it out.