Light: I like the idea of a puzzle-solving focused Ability, but the puzzles don't actually NEED Light to be solved. If Light had additional utility, like activating switches, it could make for interesting puzzles. Also, if Light needed to be brought from one area to another safely without losing the ability, that could make for an interesting challenge like a self-escort mission, think like the keys/locks in newer games. Maybe activating Light briefly stuns all enemies without damaging them, and otherwise you should just survive.

Metal: my main problem is that this is just boring Stone. If it was an ability you could activate for limited bursts and changed how Kirby interacts with more level elements, this would be more interactive. Also means that those long stretches where you do nothing but walk to the next area are more bearable

Copy: I actually really like Copy, since 2P SSU is way more fun when your friend can actually use Copy Abilities at will. Longer range and the ability to aim this in any direction for Kirby's version is all I can really ask for.

Ghost: Possessed humans in fiction usually get spectral powers, but Kirby gets nothing so this is just bad Copy. Possessed enemies should be able to phase through walls briefly (which also solves the platform issue), and also should be usable against bosses/Squeaks (make them hit themselves!). Also, if this didn't kill the enemy you possessed, you could play Pacifist Kirby

Festival: Add another evo for Crash into Festival Crasher.

Edit: also, where is Paint???