I love all the arguments on this theory so much because here's the thing; even if he is Link, he bears such a little resemblance to him. This ancient hero has long red hair, a blue body, blue feet, a bright yellow hand, and a larger body. There's some evidence suggesting that maybe it is Ganon, the Zonai hare goat, a random Gerudo, or maybe it really is just Link, but none of them seem to fully match up to the big picture. I've seen some people say that this ancient hero is a nod to the original Link sprite due to his hair (which is barely a saturated brown), but if that were true then the rest of his body would match. I mean, not even his face looks Hylian. If he were Hylian they would have at least color blocked his skin like they did with ancient Zelda. Also I thing that not many people have pointed out, is that in the Creating a Champipn book, there a description that stated that "the names and faces of the champions are unknown" which could be referring to the other characters seen here as well. They're clearly stating that because at least one character here isn't who we think they are. So something tells me that it's more likely the ancient hero is an entirely new character and not already someone pre-existing. (As much as I absolutely love the Ganon used to be a hero theory, let's be realistic here)