I see many games like DOTA 2, Chivalry: Medieval Warfare, and all of the Call of Duty games have multiple listing in the steam library. For DOTA 2 and Chivalry, these are used to provide completely separate installs of the unreleased next version of the game for testing. Would it be possible for you to offer this as a secondary download instead of as a toggle-able option on the "production" install? I personally have the space to accommodate two installs of the game. I would also like to try the new stuff, but switch back if a friend who doesn't want to go experimental wants to play.