I'd like to see someone create a living breathing world for an MMO, cities full of people (ala Assassin's Creed) which live and thrive seperate from the players. People actually do realistic jobs through the cities, food supplies rise and fall with the seasons, trade wagons go from town to town, so essentially that world could keep going forever self-sustained.
Then add your threats, creature nests and locations through the wild, caves full of monsters, etc, basically create a complex world.
Then add your players, who basically enter as trainees in the local military. They then choose promotion or service, basically entering the world of either more RTS-based civilisation management, political struggles via server-wide democracy, OR the combat side as a mercenary, soldier or even a criminal, playing a fighter/sorcerer in the conflicts of the world.
The politicians will get limited combat skills, as they do not proceed to combat to train as a fighter, however these politicians get promoted to Barons, Lords, Captains, etc, and have control of villages, towns, cities or eventually whole regions. They also get the unique ability to give other players quests (some sort of Quest Editor).
The outcome of these quests affects not just the individual combatant a reward, but increases the NPC town/city's happiness. All players benefit from happier towns, so they can decide to 'vote' for that particular player, giving him more power and control over a larger region. These politician players have varying amounts of control over the cost of weapons, gear, food, and all that sort of thing. Their challenge is to create a balanced and working society, and their gameplay is largely strategic, manipulating REAL players to gain power.
The combat side of the game plays like a traditional MMO, finding work defending a town, being hired as a mercenary or bounty hunter, or even taking to the dark side and becoming a criminal, holding up trade wagons, assassinating people or even siding with some evil NPC factions rather than the masses of towns and cities.
The combatants can obviously be hired by the politicians to carry out their dirty work. These players kill more monsters and other players than the politicians, and their main goal is money and possibly notoriety. They can fight in the arena, bribe politicians, go to war at a politician's bidding, align themselves with NPC factions, and slay monsters for fame and fortune.
The idea is that the players themselves make the storylines, and that actions taken within the world are entirely driven by player imagination.
I understand the complexities involved in creating such an idea, and the servers would have to be able to handle huge amounts of information and connections to make it work, but we advance technologically almost on a day-to-day basis, so this isn't inconceivable. I think MMOs should be divided into those that like the combat-based, stat-upgrading side, and those who prefer the RPG civilisation-management side.
Something along those lines.