I have been working on the persistent inventory system this past week and it is coming along well. I have an Item Library that can be managed from the management server web interface. Each item definition has a few commonly used fields, but you can add as many custom fields as you want. In the starter project there is a simple inventory system showing how to use the GetInventoryItems, SaveInventory, AddItemToInventory, RemoveItemFromInventory, and ParseInventoryCustomData blueprint nodes. You can expand upon this simple inventory system, or you can plug my blueprint nodes into your custom inventory system or one that you have purchased off the marketplace.
A simple character inventory system showing how to load the inventory from persistent storage, handle picking up items, moving items around, and destroying items.