I've thought that one cool thing Sora could do is have the Kingdom Hearts 2 MP bar visible above his damage percent like Little Mac's KO meter.
Without getting into too much detail on a moveset, Sora's Neutral B can perform Fire, Blizzard, Thunder (and maybe Aero) Magic by holding B and holding a direction before releasing. Fire is neutral, Blizzard is to the side, Thunder is up, and Aero could be the down input. Holding the B button charges up the magic to -ara and -aga types.
Sora's Down B could be Reflect magic which acts both as a Counter and Reflector, yet the move can't be spammed since it consumes MP.
The MP gauge depletes various amounts depending on the spell and how charged up the spell is. You can get MP back by damaging your opponent or taking damage (MP Rage). Draining your MP puts the gauge in the pink charge for a short amount of time leaving you unable to use magic. Somewhat like Robin's tome usage. Again, giving and receiving damage makes the charge go faster.
Might as well do the other two specials:
Sora's Up B is Aerial Slam. Sora does an upward slash like Marth/Lucina's. If it connects with an enemy, Sora knocks them up higher and, with a second input, teleports above them to slam them down. Is a meteor attack.
Sora's Side B is Strike Raid. Fairly basic, Sora throws his Keyblade forward and has it come back. Similar to Toon Link's boomerang. (Should it consume MP? I'll let you decide)
Sora's Final Smash is Eternal Session. Sora summons Riku similar to Robin's Pair Up. Sora and Riku float around freely and shoot out Dark Cannon by pressing the Special attack and Last Saber with the Standard attack. Part ways through, the Special shifts to Master Hearts and Standard input shifts to XIII blades. The attack ends with All's End.
http://www.khwiki.com/Eternal_Session
Here is the Wiki page for reference.
What do you guys think?