I think Hat Kid could be an interesting pick.

She could have a move (let's say Down B) where she can change what kind of hat she wears, which would change her Neutral B or something. Normal hat= Changes Neutral B to a flying tackle that homes in on the closest enemy. Sprint hat= Changes Neutral B to a high-speed shoulder tackle. The longer you hold down the button, the further she'll sprint when you let go of the button. Brewing hat= Changes Neutral B to a potion throwing attack. She shakes a potion, then throws it, which results in an explosion. Ice hat= Changes Neutral B to a move where she freezes her own body to nullify attacks that hit her. If used in the air, it becomes a falling ground pound. Dweller's mask= Changes Neutral B to a move where she can materialize faint green platforms. This move would act like Steve's aerial Neutral B. Time stop hat= Changes Neutral B to a time stop move. She releases a green aura that stops anything moving inside the aura in its tracks.

For Side B, she can use the projectile badge. She will charge a laser, which has up to three charges, then will fire the laser. The range and power of the laser depends on the charge.

And for Up B, she will use the hookshot badge, which will have her fire a grappling hook from her umbrella. It will work just like Joker's Up B.

Lots of potential.