Also other differences should be included such as the addition of a flamethrower for one team or just a distinctive weapon or set of abilities. Maybe a heavy turret for one team, and the other gets the ability to use the scope on their lmg's.
i dont know the exact details, but modifications could also be made to the aliens by having the Kharaa and another alien team. Again with slight difference (another alien class instead of the lerk or fade perhaps).
But if there were to another class, maybe a projectile shooter would be adequate.
i am interested to know what the rest of the NS community think of the Same vs Same dilemma...