Back on topic, I said that there were tripods in the movies, but no bipods.

That's not a bipod, that's a butt plate/stock that can fold under the barrel when not in use.

He's right, that's a folding buttstock.

if a sniper is prone, he can use his tripod to stabilize the gun, so why would we need a key to stabilize the aim?

Your now a Sith Apprentice congrats! *sithspammer* lol

and today's weapons have good compensators

The sway can be simulated with the cone. The cone goes wide which can simulate the sway. You hit the key and the cone become so narrow that you will have a straight shot.

Not really.  Think of it this way, on a gun with a three round burst you pull the trigger and three bullets come out in very rapid succession.  In real life, unless you were swinging wildly about like a cat with it's tail caught in a ceiling fan, all three bullets would end up in almost the exact same location.  But in BF2 all three will go in their own random direction.  A real sway would cause the gun to move as you line up the shot, so it wouldn't be perfectly where you thought it would shoot.  Once you pulled the trigger, however, all three bullets would go the same way.

Does that make any sense?  What I'm getting to is that it would be easier for us to implement your suggestions if BF2 supported (and let us control) a realistic sway motion.  It is more difficult to do what you are saying with just a deviation cone.  But we'll try and make the experience as authentic as we can