Well, Nintendo says they may put Capcom characters into Smash Brothers 4. If they really are going to do that....
Amaterasu for the next game. And good enough to be in God Tier, because, well, she's supposed to be in that tier.
Neutral special: Power Slash. Can be Power Slash 1, 2, or 3 depending on how long the special button is held, and deals 8%, 12%, and 18% respectively. This would be a melee move with projectile properties similar to Lucario's Force Palm.
Side Special: Brush Techniques. A multi-hit attack like Marth's Dancing Blade. Once initiated, the player can chain up to four hits by using the special button and control stick to use different techniques. Neutral tilt=Bloom, Side tilt=Inferno, Up tilt=Thunderstorm, Down tilt=Blizzard.
Up special: Whirlwind. Amaterasu creates a green tornado around her that traps opponents and juggles them. On the ground, Amaterasu can slide left or right. In midair, the player can tap the control stick to make Amaterasu pounce in that direction, as recovery.
Down special: Sub Reflector. This move is a counterattack and makes Amaterasu put up the Reflector to defend. For melee attacks, Amaterasu will cancel the attack, then jump up with the opponent and slam them into the ground. For projectiles, Amaterasu will smash the projectile to cancel it, and regain health. This can also be used as a very short recovery in midair.
Do it, Nintendo.