Beedle would be fun if it weren't for the fact he'd need to have a moveset based around selling ware like bait, butterflies and frogs.
I would've preferred a Beedle & Mapfish tag-team but alas, that ship has sailed.
Impa's basically a new character every installment she appears in which limit the chances of Ninjimpa every time Ms. Old Hag rears its ugly head.
Now, Ninja Impa appears less and less, so I think for Impa fans it's accepting the old hag or keep grasping for the straw that is Skyward Sword or a new Young Impa being relevant just as Sakurai decides the roster.
Keep in mind, everyone, relevance is a very big deal for first party newcomers who aren't throwback picks from the 80s. If you want to look for potential Zelda newcomers, you're best off looking at Breath of the Wild.
Unless something happens with the Smash Ballot.
Yes, I think Breath of the Wild is the game to look at for newcomers, but not neccesairly because it's the newest but because it was such a big hit.
That said, I don't think there are that many worthwhile characters in Breath of the Wild to use in Smash.
Kilton would be an ideal pick (He could use the monsters and their guts to introduce BoTW's Cooking mechanic to Smash) if it weren't for the fact he appears so "late" in the game, being more of a secret than a plot relevant character people are more likely to stumble upon, like Impa.
As for plot relevant characters, It'd be a toss-up between one of the Champions (which is hard since you can't really pick one, but not the other), King Rhoam (who has the advantage of appearing so early in the game and the NEStalgia of being "Old Man", but his role is so small he's only seen using an Axe and a Paraglider, and while a flying axe user is an awesome thought, it's a very shallow mechanic with very little room for "special attacks") and Impa, who is imo the best choice for a Breath of the Wild character.
Bottom of the barrel are Purah (with a Sheikah Slate set), Robbie (just to see the old fellah use an Ancient Chainsaw) and Beedle (who has the honor of having "frogs and butterflies" as his moveset potential)
I get really giddy when thinking about the potential of BoTW's Impa using the Sheikah Slate powers (since as Kohga demonstrates, the Magnesis rune at least is inspired by old Sheikah magic)
This is my idea: You know the hat she wears and how there are little metal Sheikah eyes on them?
Now instead of a sword, Impa would create her disjointed hitboxes by using Magnesis on the hat in order to cut opponents with an almost grinder-like hat yoyo.
The Magnesis could give the hat multiple ranges, turning it into a boomerang that can have the range of Marth's sword, but can also turn into a projectile, not unlike Link's boomerang.
That covers Magnesis, although a Special could give the player full control over the hat.
Then there's Stasis, which could find its way in the movesets in multiple ways as well.
As a Special, it could freeze the hat, turning it into a platform.
Stasis could potentionally freeze opponents as well, but like Stasis+ in Breath of the Wild, you don't have the time to build up knockback.
As a normal move it can freeze the hat in order to create a lasting hitbox, not unlike Rosalina's Up Air or Down Air.
Cryonis has multiple uses as well, though it'd require another creative liberty in order to use the Cryonis that Vah Ruta uses as well, which gives Impa access to a spinning block and a spiked ball, both made of ice.
These can be used in her Smashes as a nod to Kohga, who used spiked balls as well.
Of course the classic use of creating an ice pillar can very well be used.
Remote Bombs I really don't care about, but I suppose they can be used in a Smash where Impa creates a bomb and immediately detonates it.
Furthermore, Impa could also skip the bomb part and use the blue explosions throughout her set as well.
Of course it could act as a Down Special.
That covers all the runes, but that's not where Impa's potential stops, as she also has access to the Sheikah Heirloom Orb.
This orb could potentonally be summoned with a Special and would give Impa a new way to try her Stasis and Cryonis.
Then there's Kohga, who was once a Sheikah as well, so it's not weird to assume that Impa can summon a circle of orbs around her as well and most importantly use Magnesis and Stasis on them.
Last but not least, there are the Sheikah weapons in Breath of the Wild, which she could use as well in some moves.
I think that's not only enough potential for one set (Ass-Hattery with Magnesis) but for multiple sets each with their own feel (Blue Explosion Spellcaster, with an added ninja flair with the Sheikah Slate's teleportation) (Orb Fighter, Kohga style) (Classic Sheikah fighter with small weapons and her hat to hide them)