Kind of similar to the upcoming Gods and Heroes squad concept, but taken a step farther. Basically, this is meant to bring an epic feel to MMOs, particularly PvP, while still allowing players to be individually powerful, though there are now differing types of power beyond just the abilities of your character.
Basically, there would be two different lifepaths for players to take: They can follow the path of a Leader, gaining the ability to command several NPCs and access to skills that would facilitate that. Or they can follow the path of the Champion, which would be more akin to the standard character archetypes we see in MMOs today. Players would be allowed to switch back and forth between the paths with some limitations, but there would be significant differences between the skill sets, forcing the players who seek to have it all to spend time, effort and money acquiring the other skills and losing access to some of their previous skills, though the skills wouldn't vanish, they would just be dormant.
And it would be balanced in such a way that a Leader-type character who devotes their skills and studies towards the art of combat and hires combat-oriented NPCs could be just as effective (though in a different manner) as a Champion who has also devoted themselves to combat.
I would even extend this concept beyond just combat. It would encompass city-building as well. Champions may be great for keeping monsters and bandits at bay, but when it comes to actually building a running a functioning town, you would need leaders to command and control all the NPCs in the town.
Some of the basic skills would overlap. Everyone would be able to fight, cast magic, learn tracking, etc. But only Champions would have access to the Fireball of Mass Destruction or the Blade Dance of Doom, while only Leaders would be able to control squads of NPCs or run a store.
This method of dividing character progression into two distinct camps not only opens up interesting avenues of interaction, but also provides a variety of outlets for different types of players. Those who enjoy the sense of power that comes from personal gain would likely lead the lives of Champions, while those who enjoy crafting, socialization and other non-combat activities would lean towards the life of a leader, forming communities with like-minded individuals. Of course, there's no reason the different player-types couldn't have some crossover. Perhaps a Champion decides to ally themselves with a town, providing protection for outlying areas and functioning as a part-time sheriff. Or maybe a Leader could make a name for themselves by commanding a squad of elite soldiers that seeks out the most dangerous foes in unexplored areas.
Envision a city siege. Small organized squads of soldiers manning the siege engines, battering rams and walls, with others waiting in the wings for a breakthrough. Meanwhile larger than life heroes run about, attempting to turn the tide in either direction and engaging each other in awesome displays of power and abilities. Sounds great to me!