If Smash bros gets a Switch version, Breath of the Wild Link is likely in some form. 

He's too popular to be just a trophy though.....so how would he appear.

Would he be a costume like Advent Cloud, a alternate fighter form like Alph, or a new fighter sep from Regular Link due to his different equipments and abilities (Daruk Protection, Revali's Gale, and Urbosa's Fury seem like good move options for down, up, and something B, and Mipha's Grace could be an interesting Smash as a complete heal option). 

'Champion Link'?
'Sexy Link'?

Maybe call the new link just Link and call the existing one 'Classic Link'?

I think they'd probably just give Link a new outfit, instead of an entirely new character slot.

Yeah, he'll probably have a separate set of skins for BotW Champion outfits. Like how Warrior has the separate set for his original design, or how Wii Fit Trainer has the male set.

They'll make him with a red Nintendo Switch t-shirt and a paraglider. He would be unlocked with a amiibo or DLC. His move will be a parry attack.

He'll be one of the costume options as Link at the very least, there has to be some sort of new additions to make this version worth purchasing

Wild Link

I believe Smash switch (that is not the wii u port, and that i don t believe will happen) will revamp many of the old characters, zelda, link and ganandorf are the twilight princess models still, mario is another one that i believe will be revamped. And when i say revamp, i am not talking about only characters models, but modify half or more of the moves too.
That, i believe, would be a lot better way to give a fresh air to the game without injecting a ton of new characters on an already overcrowded game.

Completely new gameplay for botw link. A new link slot, of course, call it hylian champion instead.
Revalis gale as b up, dropping bombs and arrow while in the air, change the type of arrow, daruk protection as shield, strikes when perfect dodging, a combos with different weapons. You start with a sword and it breaks in the middle of combo and then you grab a club, it breaks then you grab a spear, etc, all in the same combo. Sometimes he can drop weapons. About the customizable options, cryons, stasis, etc.

All his weapons will break like glass, it'd be impossible for him to win.