I don't think its going to be a single creatable character, more like
everyone on the roster can customized. Let's take Mario for example. In the 1st 2 games Mario's vB was Mario Tornado. In Brawl it was FLUDD. Which of these 2 should be the vB in SSB4? My answer is
both & the player gets to pick which to use.
Now let's take that idea further, where every move"slot" has multiple options to choose from:
B
-Fireball (high damage)
-Ice Flower (makes the opponent slower for about half a second)
-or star bits (rapid fire)
>B
-Cape (defensive)
-Hammer (melee offensive)
-Red Rocket (ranged offensive)
^B
-Jump Punch
-Wing Cap (greater recovery, non-damaging)
-Charged Jump (greater recovery & damage but requires charging)
vB
-Mario Tornado
-FLUDD
-Rock Mario
Final Smash
-Mario Finale (single shot)
-Mega Mushroom (timed transformation)
-Yoo Who Cannon (multiple hits)
The player selects which ones he wants to use in his active moveset , such as
Emphasis on defense build
B: Ice Flower
>B: Cape
^B: Wing Cap
vB: FLUDD
FS: Yoo Who Cannon
or,
Emphasis on offense build
B: Fireball
>B: Hammer
^B: Charge Jump
vB: Rock Mario
FS: Mario Finale
& saves the build to his profile so Mario will always be set to it.
This concept of moveset options would be applied to every character on the roster. All of Link's acquired items through the years including different arrow types, Bowser's spells in SMRPG & M&LBIS, Fox's weapons from Assault & skills in Adventures, Pit's newfound arsenal, the possibilities aren't endless but are certainly higher than ever for SSB. & yes, Miis are entirely a possible inclusion for this as well.
Now with all that said, that would only be HALF of the game's customization features. The other half,
The return of passive stat boosts & abilities. In Brawl they only affected SSE but in KIU they carried over into multiplayer. This can pretty easily be applied to SSB4 too.
The Wii U version would be the vanilla version, all characters have pre-set moves. In other words basically the same as past games. This is the genius of SSB4: Players who simply want more of the same will be content with the Wii U version & need not care about the 3DS version at all............................until they go online & get their ***** kicked by a Pichu with Iron Tail & a resistance to knockback & wonder to themselves what just happened. That's when they begrudgingly put down $200 on a 3DS & the other version just to stay competitive.
Character customization ain't just a gameplay innovation, its a devious marketing scheme!