I've avocated the use of a modern-day AGC (automatic Gain Control) on playback as a way to diffuse the volume wars from some time now.
Though I'm not positive I'm keen on a single standard open-source algorithm for doing this. I'm more of an open-market advocate thinking that letting the manufacturers compete on the AGC quality will yield better results than open-source collusion.
There's also the need to coordinate the use of such AGCs as a means to diffuse the volume wars. I see no signs thus far that "RG" has any effect on that. I have proposed that an AGC circuit (or software) include the ability to read a data bit on the recording that can automatically tell the AGC whether it is the artist's preference to use AGC on a given song or not (the user could always override this, but it's a good defualt option). For example, an album that has been properly mastered by a pro for non-volume-war listening will have the proper relative playback volumes already in the production, and they will not necessarily match what the AGC algorithm "thinks" is correct.