Masked Link
Chance: 5%
5% minimum.
Little reason to add him now, a 3DS remake and DLC for a spinoff game aren't the most exciting achievements. Would be a third Link, which is pushing it. Even as far as Links go, the one that fights with masks specifically isn't especially noteworthy. He may be the same one from Ocarina of Time, but that's more of a fun fact than anything relevant to a moveset.
Speaking of movesets, I'm assuming the character being rated is either the one from Hyrule Warriors or one that uses all the transformation masks. I wouldn't think Sakurai would want to use the Hyrule Warriors one in the first place, Link 2-handing a sword is hardly an exciting prospect and Fierce Deity as final smash would limit the "mask" aspect to an optional item. If the Fierce Deity aspect was part of the normal moveset, perhaps as something you build up to over the course of a fight, that would be a more viable approach. At the same time, that's hardly the best way to represent Majora's Mask in a playable character. Can't imagine Sakurai would spring for anything less than the full Deku Scrub/Goron/Zora package.
Transformation characters are gone as far as we know, even if it was for technical limitations there's no point in bringing the mechanic back. If different forms only appeared for certain moves, there'd be no way to animate the transition well. It'd look terrible if every other attack featured Link pulling out a mask, slapping it on, having a painful transformation sequence for 5 seconds, doing the actual attack, removing the mask, transforming back, and slipping the mask back in his tunic. If instead of this Link had 4 (5 with Fierce Deity) movesets and could switch between fully-realized characters at will, then Link #3 from one mainline game, it's remake and a spinoff's DLC would be the highest effort newcomer in the history of the series.
Want: 0%
It's hard to think of many relevant characters I'd like to see less. Would either be unfaithfully represented or take up quadruple the development time of any other potential newcomer. Even as a fan of Majora's Mask (and the transformation mechanic in particular), I can't justify sucking up that many resources.
Double abstain from triple trouble.
Nominations: Nikki x5