Have one person host a game over the internet, (we have not done any dedicated servers) where you can kill an enemy and take their launcher (as far as I know it's applicable to all launchers, but I know at doesn't work with OPFOR AT launchers).
Have another person join the game and pick up the loaded launcher, when they equip the launcher it should be empty even though it should have a rocket already loaded into it.
You can also have the host pick up the launcher first, make sure it's loaded then drop it so the other player can pick it up, then when the other player picks up the launcher it'll be empty.