Complex Inventory

Guys, i want to create inventory system wich can be used in multiplayer

Player can pick up backpack and there will be some inventory grid
player can have pockets and have some slots
can pickup jacket with some grid slots

and when player kill enemy he can loot him where can be same slots

how better build inventory like this?

i try to make it, but have some problems when i try to open some item with inventory inside backpack, so want to make something different
hope for your help or advice, thanks