I've always felt that Sakurai neglects the Zelda series. In Brawl, Toon Link was the most clone of all of the semi-clones, to the extent that many of Tink's attacks were coded wrong (kick instead of shoulder) because they didn't bother to change the coding from the parent. Come Sm4sh and Zelda still hasn't got any newcomers but now Zelda's final smash was stolen by an interloper, and Link and Tink weren't even able to get different crowd chants.
I'd really like some of the one-shot characters. Marth, Ike, Roy, and now Robin and Lucy haven't really been relevant in Fire Emblem, but they get added all the time, meanwhile Zelda keeps the same characters. I'd also like if any new Zelda characters would rep their respective games so that Link and Zelda could stay relatively the same (Zelda is doing quite well representing Ocarina of Time, whereas Link is pretty well a general Link from all of the games). Honestly, Tink should have more of a Wind-Waker moveset to rep that game and to declone him a bit, and Ganondorf should discard some of his more blatant Falcon moves to rep a general Ganon/dorf moveset.
Midna's been one of the biggest names in all of this, and she could easily rep Twilight Princess herelf. After Hyrule Warriors, moveset is not an issue anymore. The same could be said of Fi, but Ghirahim is the name more often bandied about, which would also be appropriate and give us another villain. Same with Skull Kid and Majora's Mask, but there are also calls for Young Link with a new mask moveset, which may be harder to implement. (Yes, Skull Kids the race have appeared elsewhere, but people don't want the rando you get a Piece of Heart from in Ocarina, they want the one wearing Majora's Mask, who was only in one game)
As for Breath of the Wild, that would be tough to get one rep for all of them. Sakurai doesn't like to add characters with no future (or at least he holds this rule for Zelda and not Fire Emblem) and all of the champions are dead, so that presents a problem. I can't see all four getting in (but how awesome would that be), and just putting one in would feel like breaking up a set. True, each race does have their own versions of each weapon style, so it's conceivable that one champion could represent all four (get all four champion abilities as specials, use various weapons as normals, and a divine beast final smash), but again, which could be considered more important than the rest? A fun compromise would be for all four to share a slot and moveset, but while scaling Urbosa, Revali, and Mipha to fit, Daruk would not work well in that case. Or, another character could be added to use all four champions specials and summon their spirits as necessary (Kass, or go with a sheikah like Impa here).
Trying to place one champion over the others is also tough based on timing. If the roster was planned around summer of '16, that means that he had access to the concept art and maybe some hints from the directors about their abilities and personalities, but not their reception. I think the directors were surprised how popular Sidon ended up being. That also makes it much harder to predict what will happen.
If it were up to me, I would 100% put Zelda one-shots in, and in this order:
- Urbosa (BotW)
- Midna (TP)
- Ghirahim (SS)
- Revali (BotW)
- Skull Kid (MM)