What characters do you hope get a new Final Smash in the next game? Personally, I want Daisy to get a Final Smash based on the Elephant transformation from Wonder.
Revert all Final Smashes that were previously transformations back into transformations, and buff Giga Mac to function properly.
Kirby should get Hypernova. I know Big-Rig Mouth is more relevant but I always found Hypernova to be really cool.
Steve should get a new Final Smash called Creative Mode, a transformation Final Smash where he flies around the stage and spawns active TNT blocks, Creepers, and harmful Splash Potions.
Daisy should get a Wonder Flower Final Smash that triggers one of several random effects like summoning a horde of Bulrushes to run across the stage, turning all opponents into Wubbas, or creating a Piranha Plant festival that causes them to spawn on-stage as they sing to the music and attack players.
I could go on but I'd be here forever. Point is, I need more creativity than pressing a button and watching a cinematic of someone die. As long as we get that, I'm happy.