errrrrrrrmm.... i'd probably make a sort of MMOTFPS (i challenge someone to work out what that means
), which would have around the same number of players as M.A.G (256 players), and players will be split into squads of about 4-8.
Tach side will also have one player acting as the general of the entire team, who can give objectives to the squad leaders. Squad leaders can also request certain things from the general (such as reinforcements, which the general can provide by requesting another squad to support them).
There should be one primary objective (e.g., capture the enemy general, who can be inside a bunker on each side of the map), but while each sides primary objective should be the ultimate goal, the general can set secondary objectives that will help to reach that primary objective (for example, i turret may be blocking the way to the objective - the secondary objective of a squad/squads could be to eliminate that turret so they can get to the primary objective.
Of course there would be class system in place, and a squad would work best with at least one of each of the classes within it, as they could support each other.
Vehicles could also be designed with this in mind - each designed to work best when manned by a crew of a single squad, or maybe even with specific classes occupying a specific role within the vehicle. (e.g., a heavy weapons class using the weapon mount on a APC could increase the accuracy and power of the gun, while an engineer class driving might make the APC go faster, and be more resistant to damage)
To add to the originality, maybe there could be more than 2 sides? considering the number of people in a game, maybe there could be 4-6 sides, and the generals of each side could freely form alliances with different teams to gain an advantage over another.
basically the game i make wouldn't have one very large original factor to it, but many smaller design choices within it to make a very unique online experience.