Pockets for leather armour but they work like bundles.

Basically when wearing leather trousers or chestplate it grants you say 7 extra slots (four for trousers, 3 for chestplate). Pockets could work like bundles, each pocket being able to store a stack of 64 with that stack being able to be made up of 64 of the same item or different stackable items e.g 32 wheat seeds and 32 melon seeds if you so wish). To access a pocket you would simply open your inventory and the items stored within would be next to the current inventory but disconnected from the default slots (like the offhand is) so they are easily identifiable as your pockets. Removing the armour would not remove the items from the pockets so you would in effect be able to make armour stands have an inventory if wearing the armour containing the items. If your armour as an item despawns any items within would be dropped as items like a shulker box. This suggestion has taken consideration into mobile players as well.