There was one game that conquered this, Freelancer! Now I have told you all many times that I dislike old games because the new ones look, feel, play, and run better then the old ones, but Freelancer was damn good to me for a while. I started playing it in 2004, a year after it was released, and the mod community had spread like wild fire. I found a couple mods that I liked for online play but one had made everything that you could imagine. they had thrown in a economic adjustment so as you traded to a certain area they would pay you less and less for it, your guild could have a bank account allowing people to see your stock and invest in your guild and then sell when they wished. They had made territory for the guilds and when you went to war you had to have a guild member remain in the area for 24 hours, and if your member was killed they were no longer allowed to return to the battlefield. They also would release a weekly news report on a podcast for everyone to listen to what had been going on with guilds and business. But, most importantly of all, the forum was a strict RP forum. You would delegate on the forum, purchase supplies or get a business to make a delivery for you. There were times where I rather be on the forum then in the game.
So why not have that strong RP sense, but with the forum on the game itself. make it to where you can delegate in game, where people's characters and guilds are there for more then just level up and PvP. I loved Freelancer sheerly for the fact that my character had a role in the game. My character could make actual important decisions. I think that would keep a lot more people playing then just another MMO.