the game already has nearly everything when it comes to nationalities and their stereotypical roles in the team:
there is a russian, a frenchman, an australian, a scottsman, a german, an american, a texan, a (bostoneer?), and an unspecified one (though i think the pyro is mexican or dutch or something).
then, most of these guys have a role that fits their nationality: the slow and stupid russian, the deceptive and suave frenchman, the aggresive and explosive american, and the evil doctor with the german accent.
so if there would be another class, it would have to be different from these nationalities, and have a stereotypical role. my proposal: a chinese dude
the chinaman is not that good in battle, and has very little ways to kill. his primary weapon would be fireworks, kind of like a flare gun/rocket launcher that burns and blinds enemies from afar.
he would be able to give players buffs by giving them chinese herbs. however, the primary purpose would be distraction and deception. maybe the chinaman would have a PDA-like device, which he uses to create fake team members and objectives, smokescreens and signal fires, and maybe he'd use it to blind sentries and sniper scopes
oh, and his melee weapon would be something like chopsticks, or maybe a hand halberd (look it up), and his kill taunt would be the creation of a fake dragon with his PDA, that gives nearby enemies a heart attack
