She's a Goddess incarnation in Skyward Sword. Why the **** should she turn into a ninja?
Unfortunately for you, being a "Goddess reincarnate" doesn't mean anything as the only thing she's seemingly
capable of doing is sleeping in a crystal.
Otherwise, she's just a typical mortal.
So again, since Zelda apparently should have only things that are "iconic" to her in Smash, she has literally nothing to use, meaning she should not be playable.
Aside from that, being known as a goddess reincarnate is not that iconic by your logic, as it's only touched upon in ONE GAME. None of the future Zeldas were goddesses, just
ancestors of a mortal who USED TO BE a goddess.