I agree with Super Sailor Yue, a petition for the a Tsubasa now would be rather, um misplaced. One there is not enough done in the Manga yet for a Season 3, unless they drag it out. Two: Later things in the manga will get more eviler, and darker, so it would be cut and slashed, also, even one of the CLAMP members said Fay's past would be hard to animate. and three: if the rest of TRC gets animated, which I am sure it will be, will most likely be OVA's, or OAD's.
I don't mean that in a bad way at all, so please don't be hurt by it.
But FAIsPrincess petition's are good sometimes, just as a dream for the fans, just I've only seen one Anime won over by a petition, "BIG O".
A petition I would go for those is the Drama CD's turned either into an Anime or moive/ova. Hehe. But then agian that is a dream too.