Pocket enchantment (Deep Dark loot)

You could add a new enchantment to the game. This one would be "Pocket". It would have 3 levels. Each one will provide 1-2 slots in the inventory. This enchantment will be only available for the legging part (which don't have a lot of enchantments and enough love yet I think). If we take out our leggings while having some stuff inside the new slots, the items will just be thrown on the ground.

To keep it balanced, it would not be obtainable by enchanting tables nor villagers, and just like the "Soul speed" enchantment, it would have to be looted. But where ?
In 1.19 comes "The Wild Update". I think having this book in the Deep Dark chests would be a great motivation to go in there, while both solving a bit the inventory issue and being a late game feature so we cannot have it soon for the progression system.