Glad to see K Rool being in Brawl seems to be a consensus here. I dunno if it's the slowness and projectiles or what but he just screams Brawl to me. Maybe that's why Diddy likewise screams Melee to me, being one of the fast, combo-centric archetype characters; and Melee is where that archetype is at its strongest. K Rool definitely should have been in Brawl and Diddy in Melee, which would hopefully result in Ultimate including either Dixie, Cranky, or Funky, but I digress.
I also wish Wario had been in Melee, because his Wario World moveset just strikes me as perfect for Smash, with room enough for a few of the moves to also reference the Wario Land games. Give him Bike as a new side B in Brawl, along with the biker alts, to still reference Warioware, and you're good to go!