This is kind of a sore point for me.  In BF2, instead of simulating a real swaying motion, guns are given a "cone of deviation" (note that this is not at all like the cone of silence from Get Smart).  As you fire the gun, it randomly deviates from the direction it is actually pointed.  So if you were lying completely still, with a tripod and not breathing, heartbeating or even thinking, you're still not guaranteed to hit a stationary target you're aimed at, since it randomly deviates from the place you've aimed.  This obviously makes no sense with lasers, since they should always fire straight.

BF2 does take into account motions and positions, so the cone tightens when lying prone, and gets really wide while running.  I'm saying all of this because it might affect whether or not something like you mentioned would ever make it in the game.  I know we can adjust the deviations so that it always fires where you're pointed, but I'm not sure if we can control the swaying of the soldier and change it when in different positions.  SCHRifle may know more, but I wouldn't get my hopes too high.

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