I want Anju's Grandmother as a Jigglypuff echo.
But jokes aside, Zelda is a franchise with counless possible unique characters for Smash, it's really underrated/underrepresented.
First of all, Young Link should be decloned. It's the most unique version of Link, with the mask transformations and the Ocarina spells, Fierce Deity Link as his final smash... they can make a wonderful character, but it's still stuck as a clone.
Then, you have:
Classic Ganon
Tingle
Impa
Vaati
Ghirahim
Tetra
Midna
Skull Kid
the BOTW champions
And a bunch of more obscure but still cool characters from other less popular games, such as the Oracles games.
It's the franchise with the most wasted/unused potential along with the Kirby series.
But back to jokes, I'd like to se Error as a fighter, a pixelated character who fights by using graphical glitches as attacks.