I would create lots of single player dungeon out in the wilderness of azeroth. All the quests would revolve around these single player dungeons. The quest would be objectives rather than the typical fetch ten of this kill ten of that type quests. I would set it up so that when you are questing you are phased out into your own azeroth with the option of letting other players join you or you them. I would make the mobs and the resources denser. I would set up followers who are like bots that you can hire, healer, tank or damage dealing bots/followers. You could hire a small party of them.