Don't release it near Diablo 3. jk
1. Have one very large inventory for each human player, rather than individual inventories for npc's, and huge storage.
2. Implement some sort of optional auto equip that can be customized to prioritize what stats are important for your characters. The most boring part action/rpg's with huge amount of loot is sorting through all the stuff I pick up and deciding what to replace. Although I like developing a party rather than just one character, this downtime it greatly lengthened if you have to manually multiple characters.