Here's how we can make it work
This trick can keep it from being too many Links. Masked Link would transform into the various Links, but not in the manner of Pokemon Trainer. He would transform for a short time, long enough to perform an attack and shift back. In essence, some of his attacks would transform him for the duration of the attack, allowing him to transform without having to get more move-sets. The transformation would change Young Link's size, but upon being hit, he would revert to being Young Link and react accordingly; in an example, using an attack that transforms Young Link into Deku Link makes him a bit smaller then normal, but will not make him a lightweight if he gets hit, and conversely, he would not become incredibly heavy if hit while doing a Goron Link attack. This kind of move-set would allow us to have Young Link the Majora's Mask goodness, while retaining a reasonable number of movesets (Fierce Diety Link would still be a Final Smash). I belive that this is not so far fetched an idea, nor is it far removed from Majora's Mask itself, because quick shifting between forms was a fairly useful trick that helped throughout the games (or at least against some enemies).
I think this is the perfect time to show off the move-set that came to me in a flash of inspiration.
Masked Link:
Stats: Same as Young Link
Appearance: Same sort of changes that were made between Ocarina's Young Link and Majora's Young Link apply. He's got some new gear, a metal shield, and the awesome-to-look-at Razor Sword.
Attacks:
Ground A moves:
A, A, A/AAAA etc.: Left Slash, Right Slash, Stab / Illusion Stab combo: Same moves as Young Link in Melee.
Ftilt A: Drop Slash: A vertical slash from forehead level to stomach level (reletive to YLink of course)
Utilt A: Arc Slash: An arcing swipe above Young Link's head
Dtilt A: Shoelace Slash: A swiping slash at the feet
Fsmash A: Goron Punch Young Link Shapeshifts into Goron Link and charges up a burning right hook that, while slow, is incredibly powerful and includes a few invincibility frames. Enemies are launched in a fairly horizontal arc.
Usmash A: Twin Zora Swipe: Young Link transforms into Zora Link and swipes twice with his fins. The first swipe can hit people in front of him to begin the move, and the second is more limited to above his head and launches foes straight up.
Dsmash A: Deku Tornado: Young Link transforms into Deku Link and performs a variation on his spinning attack, drawing foes in to be hit multiple times.
Dash A: Deku Spin: Deku Link performs his spin attack in a dash. The move is far less powerful then the aforementioned Deku Tornado, but it still hits multiple times, and Deku Link loses no momentum doing it.
Air Moves:
Nair: Zora Kick: Young Link becomes Zora Link and does his normal air kick, but by transforming, has a longer kick range then is normally expected.
Fair: Tumble Slash: Young Link does a forward flip in the air, slicing foes in front of him.
Bair: Zora Double Kick: Much like Zora Kick, Young Link becomes Zora Link and performs his old back kick, using his Zora Form to gain extra range.
Uair: Sky Stab: Much like Link, a stab straight up into the air:
Dair: Sword Plant: Young Link performs what has become his signature move, chance of burning included.
Grab moves:
Grab: Golden Hookshot: Masked Link has an extended grab, using the golden Hookshot from Majora's Mask.
Grab Attack: Hilt Bash: Young Link hits the foe with the hilt of his sword.
Fthrow: Stomach Stomp: Young Link kicks his foe in the stomach, launching them a short distance.
Bthrow: Reverse Zora Kick: Zora Link drags the foe around to the back, stabs them with a fin, and launches them with a kick.
Uthrow: Deku Pop: Young Link tosses the foe up, and then Deku Link pops into the air, head butting the foe into the air.
Dthrow: Goron Slam: Goron Link curls up and slams into the foe while they lay prone on the ground.
Special Moves:
Neutral B: Magic Arrow: Young Link draws his bow back, adding magic power to the arrow as he draws it. A short charge (whic still includes a horizontal trajectory) makes it a fire arrow, a bit longer then the "normal" full charge makes it an Ice Arrow which can freeze enemies similar to what the Ice Climbers can do, and any longer then that makes it a Light arrow which is even stronger and keeps moving through foes and obstacles.
Side B: Goron Roll: Young Link becomes Goron Link, curls into a ball, and rolls across the stage covered in spikes. The spikes deal some good damage and are disjointed hit boxes, making the rolling Goron hard to hit.
Up B: Deku Flower: Young Link becomes Deku Link, who pops higher in the air, and produces a pair of Deku Flowers that he uses to catch the wind and float with. Pressing the attack button will drop a Deku Bomb which functions like the Deku Nut item.
Down B: Zora Lightning Field: Zora Link goes into a defensive stance and surrounds himself with an electric field, zapping those who get too close. The move diminishes in size with use and recharges with non-use, much like Bowser's Fire Breath.
Final Smash: Fierce Deity: Wait a minute, surely this move is restricted to boss rooms, right?* After using the power of a Smash Ball, Young Link becomes Fierce Deity Link, and becomes much stronger then his original self, and gains new moves to boot (Fierce Deity Moveset to come)
*You don't have time to ponder that question, as Masked Link has just grabbed a Smash Ball
Taunts:
Lon-Lon Milk
Zora Link strumming his "singing guitar" (which plays the "jam session" music)
Goron Link looking confused and going "Owoh?"
Deku Link staring at a flower.
I believe that with this move-set (or one similar to this but removing moves that would make people cry "CLONE!") Masked Link would become a viable alternate Link, but with enough uniqueness to be his own character, and without burning 5 move-sets to do so!
