I wish that the ongoing Gundam Wing Endless Waltz: Glory of the Defeated manga was being translated into English, because so far it's doing a very good job of incorporating just about all of the backstory and tangential canon material from the various side stories into a single running plot. The artwork's gorgeous, too. I don't know if anyone's scanlating it, though, but it's worth looking around for. Based on where the most recent volume (11) of manga left off -- around EP 40 of the anime, after Relena's coronation -- there's at least three more volumes' worth of material to go through.