Since I can't actually click on all classes BUT the Operative this time, I'll simply choose Soldier, then kindly remind you there's a sticky called "The Unofficial Brink Poll" or some such.
Though as mentioned, in the spirit of the next week, I really can't scorn the utter anxiety anyone on this forum might be experiencing right now as they make their individual "what class" and "what body type" polls.
We've beaten every scrap of info we have to death, and with the release a week away, it's like we want to speculate, but we know we won't have to in just 8 more days!
There's plenty of threads like this one, but in the spirit of the next 8 days I'll play along.
I think operative would be my class of choice in the final version of the game, I just dig stealth more than brainless rushing, or staying back with a turret.
While FF does discourage TF2 spy checking, medics would probably make the next best spy hunters outside of actual operatives. Shoot the leg, throw a pack, or continue shooting. Really depends on the result of shooting someone in the leg.