Princess Hilda
Chance: 70%
I think she has a pretty decent chance of appearing as Zelda’s echo. Although she is not talked about too much, she has two big points in her favor:
The first is that Zelda’s design is straight from ALBW, so they already have something to base her model off of since they look incredibly similar. I'd even argue that Hilda looks more like her non-echo counterpart than the rest of the currently revealed echos do (aside from maybe Dark Pit).
The second is that none of Zelda’s alts make reference to Hilda:
And no, that 6th black alt is not based on Hilda in the slightest. There are a lot of differences between the two like Hilda having red eyes, a green belt, a red gem on her crown, much darker hair, etc. If anything it is more based on the dark Zelda alt from SSB4.
Sakurai obviously looked towards ALBW when making Zelda’s design in Ultimate, so he most likely saw Hilda in the process and how similarly she looks to Zelda. In a series where color palettes have been used to make a character look like someone else from their games (Lucas’ Claus alt, Captain Falcon’s Blood Falcon alt, etc.), it feels odd for Zelda to not have the most obvious color palette reference they could’ve done. When Samus was first shown in Ultimate, she was noticeably missing her Dark Samus alt from SSB4 and we all know how that turned out.
The idea of Hilda being a Zelda echo also makes complete sense lore-wise since Hilda is literally Zelda's Lorule counterpart. Their moves would be the same for the most part, with Zelda's down-B Phantom being replaced with either Yuga or Ravio (or just a completely new move altogether). As for incorporating Hilda’s staff, they can either remove it completely or give it to her and let her borrow some of Palutena’s tilts (I’d prefer the latter). It might seem farfetched to some, but as seen with Dark Samus’ general floating animations they can easily tweak some of Zelda’s animations a bit to suit Hilda.
EDIT: Since people are saying Hilda isn't popular enough to be an echo, remember that basically no one requested Richter. Also for what it's worth ALBW is one of the most highly rated 3DS games of all time. Not to mention Hilda's use of her staff could help differentiate herself from Zelda.
Want: 100%
I absolutely loved ALBW and Hilda is easily one of my favorite Zelda characters. Her motives for her actions were justifiable and I loved how her story ended. As said before she could function as a Zelda echo while possibly also incorporating some of Palutena’s moves such as her tilts that user her staff.
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Impa
Chance: 35%
She is a pretty popular request and could possibly work as a Sheik echo given they use her SS or Hyrule Warriors design. I’m not sure if they’d actually go through with it though.
Want: 65%
Impa is easily one of the most important characters in the Zelda series so she is long overdue to appear as a fighter. That said, if she were to be an echo of Sheik then I wouldn’t be too excited since I don’t really like using Sheik. If she somehow makes it I hope she’s a bit more on the unique side.
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Nominations:
Kyo Kusanagi x5