Well, it isn't some theoretical construct... it's being done now with KDE and hasbeen working just fine. It stays in updates-testing until you decide to push it to stable. KDEfolks by and large want the updates as fast as possible. If the GNOME folks would liketheir updates to age for six months, they can just keep them in updates-testing. Seemslike we're just making this more complicated than it is.