Okay here is a crazy idea maybe a trading system or the option to give loot to other players. One thing I like in borderlands 2 was maybe half the time I played online. Other players would just run up to me and just give me stuff. Oh hey your using maya take this mod it well help you level up faster. Or look you joined a game in progress player runs over and just gets me stuff… I do trade. I myself do this all the time to lower level players… Just give them guns and mods.
I mean this does sound stupid hard to do, but yea just putting this idea out in the world. Maybe have it in the character select screen. Have a loud out just for sending to other players stuff based off the character type. Oh you picked a attacker here is gear for damage or heath.
Just my two cents .