Yeah, but nobody really uses ruby outside of it being a color or gem.
There's no ruby ranking, or ruby standard, or describing a moment or memory as ruby [rubius? I don't even think there's a form of the word that can actually equate to gold > golden]. That's why I liked the Golden name so much, like yeah, this is the golden version of P4. I'd still like it for the subtitle to at least have some kinda connection to the theme of the game or something and be the same kind of adjective as before. Heck, I'd take Red Alert over just Red since you could connect it to the ever increasing stakes in the game.
EDIT: That'd even work for the palace system when you finally get the target on edge and the whole place shoots up to 99%.