I think Masked Link is extremely unlikely considering we don't even have a Majora's Mask remake at the time. I would however be extremely pleased if we got a Masked Link nonetheless.
My own two cents for a moveset:
Deku Link
Neutral Special: Deku Bubble - A chargeable projectile that moves erratically in its destined path. Tilting up or down while charging changes the angle at which the bubble is launched.
Side Special: Deku Leaf - A large leaf that does no damage but blows the opponent back with a large gust of air. If used in the air, Deku Link goes flying backwards in the opposite direction of the gust, making it a decent horizontal recovery.
Up Special: Deku Flower - Deku Link dives down into a flower underneath himself. If used on the ground, it can be charged to launch him extremely high, possibly at the highest distance in the game, to allow him to slowly drift down with a pair of rotating flower helicopters. During this, he can press his special button to drop Deku Nuts which function exactly the same as the item in Brawl. However, his flowers eventually die out, leaving him completely vulnerable on his fast fall down. Additionally, it cannot be charged in the air at all, giving him only a minimal boost if used as a recovery. The flower-copter effect still take place however, making it compliment the Deku Leaf for giving Deku Link one of the best horizontal recoveries.
Down Special: Mask Change - Changes Deku Link into Goron Link.
Goron Link
Neutral Special: Megaton Hammer - Goron Link takes out a hammer and smashes it on the ground in front of him. It acts similar to a single damage interval like Donkey Kong's Down Special in terms of range and knockback. If the opponent is directly underneath the hammer hitting the ground, it buries them into the ground.
Side Special: Goron Roll - Similar to a heavier version of Sonic's Spin Dash, Goron Link curls up and begins spinning in place. Releasing the special button sends Goron Link forward, rolling around with spikes at an alarming speed. If the special button is pressed again immediately after being used, Goron Link rolls without spikes, which does no knockback and leaves him vulnerable to attack, but gets him across the stage rather quickly.
Up Special: Ground Pound - Goron Link heaves himself upwards curled up into a ball. It functions similarly to Dedede's Up Special, but has less height in general in exchange for a much more fast and powerful downwards fall.
Down Special: Mask Change - Changes Goron Link into Zora Link.
Zora Link
Neutral Special: Zora Boomerang - Zora Link shoots his fins like boomerangs. It is weaker than Link's and Toon Link's Side Specials, Zora Link shoots out two at once and each fin moves much faster than the other Links' boomerang.
Side Special: Hookshot - Zora Link whips out a hookshot and shoots it at an approximate 30 degree angle. If it hits an opponent in the air, it will pull them in, leaving them vulnerable to be combo attacked by Zora Link. This is especially useful as a high-risk edge-guard in the air, as it can lead up to meteor smashing an opponent trying to recover. If the tip hits a wall, it latches into it, letting Zora Link take advantage of it the same way Link and Young Link did in Melee.
Up Special: Electrical Aura - A veil of blue light surrounds Zora Link as he crackles with electricity. Zora Link spins upwards into the air as if swimming, having some horizontal control as he does so. Does a good amount of hitstun to the opponent, meaning that an opponent hit at the very end of the recovery is left vulnerable to a smash attack.
Down Special: Mask Change - Changes Zora Link into Deku Link.
Yes, I am fully aware none of the Link forms use a Deku Leaf, Megaton Hammer, and Hookshot. Since Smash Bros. is not canon and each of the items seem fitting enough for them, however, I figured it was a justified crime. Deku Leaf already has Deku in the name and fits in with Deku Link's natural moveset. Megaton Hammer was acquired in the Fire Temple in Ocarina of Time, meaning that I think it wouldn't be too out of place for bulky, powerful creatures like the Gorons to be proficient with a bulky, power weapon like the Megaton Hammer. Hookshot itself follows the same logic for the Zoras, in that it was found in the water dungeons of OoT, MM, and various other Zelda games. They fit as specials and help differentiate the moveset from other Masked Link movesets, so I figured it was to my advantage to use them.