The Cape/Flying ability was in Kirby's Adventure as well. But it should not replace the cutter, which is one of Kirby's better known abilities. As is the hammer and the stone (which is why they're his B attacks).
The 'yellow boomerangs' are just the 'normal' form of what Kirby's UpB is based on.
Kirby already uses his Fighter attacks, that what his normal A is based on.
And Meta-Knight would not use the cutter as his UpB. If they don't make up one from scratch, they also have an attack that Meta-Knight used in Kirby Super Star that would prefectly as his recovery.
The 'yellow boomerangs' are just the 'normal' form of what Kirby's UpB is based on.
Kirby already uses his Fighter attacks, that what his normal A is based on.
And Meta-Knight would not use the cutter as his UpB. If they don't make up one from scratch, they also have an attack that Meta-Knight used in Kirby Super Star that would prefectly as his recovery.