Is Saber eligible for Smash? AKA the "answering to 'but she's an anime character'" section:
Well, first off is that, despite what her series is better known for in the West, she did debut in a game, the original Fate/Stay Night is a Visual Novel for computers and was later re-released in consoles like the PS2. Her first, and currently, only appearence in a Nintendo console is Fate/Extella, a Musou-styled game, as a "secret" unlockable character.
As such, she checks off the two universally-agreed-to requirements for Smash. Also, should you believe a Visual Novel is not a game for whatever reason, please refer to Fire Emblem the Phoenix Wright thread.