Personally, I'd like to see a double-down on the Vanguard vs Drifter choice. I think it would be really cool if the factions could actively fight each other and only characters of the same faction could fireteam. For D3, it would be nice if there was a separate hub for corrupted guardians who were exiled from the City, maybe their own shared (or individual) Throne World(s)? What would you guys like to see?