I have a suggestion, and I think Its a decent one.
Victini over Pikachu. Essentially a clone, really all it needs is to replace the electric effects with fire effects, and maybe change his Neutral B, Side B, Down B, up tilt, up air and up smash to something different.
I suggest him over Pikachu because for one thing, in the Pokemon games, Victini can already learn a lot of the moves that Pikachu learns (lol Victini learns both Thunder/Thunderbolt, has a Psychic equivalent of Skull Bash, learns Quick Attack, all that good stuff). Secondly the moves that need to be changed can be different enough to make a new character with a different style. His up smash could be a pillar of flame for example, and his up air could be something like he moves his finger in the same angle that Pikachu moved his tail, but instead of a gimp tool, its a juggling move and depending on where you hit with it, you could get vertical or horizontal KB. And his fair could be a single strong hit with his ears a blazin'.