Deep Dark Unique Loot Idea: Consumable inventory slot

Over the years all Minecraft players alike have complained about the size of the inventory. So, let us solve it ourselves. Introducing a new consumable item the inventory slot/ancient slot ; name to be decided. This item would be found in the new deep dark cities and when consumed, it adds an extra inventory slot to the player who consumes it.

How would this affect the current inventory? An idea is to add an icon like the recipe book in the inventory to access these extra slots so that the current inventory is not affected. This item slot will also not be removed upon death since it was  so dangerous to even get the item( referring to the deep dark) but will still drop the item it was holding like a regular inventory slot.

The deep dark is a biome that should influence late game and early game players alike to want to go there and this unique loot idea seems to fit all categories and provides a solution to current problems the game is facing.