One stage I wanted to see was a Mario Clash one where it was 2 layers like Jungle Hijinx But there would have been much more interaction between planes. The mechanic died as quickly as it lived so never mind on that part.
On the other hand there are so many stages I'm not sure what would be unique or nessesary.
-Air Rally (Rhythm Heaven Fever): 2 planes next to each other playing badminton, sometimes after a delay, one will zoom off into the distance dropping anyone still on it, sometimes the birds from flock step appear and can be used as platforms too.
-Temporal Tower (Pokemon Mystery Dungeon 2): Peak of the tower, starts out fairly basic, but Primal Dialgia is a stage boss, before Dialgia appears, the stage warps into the future where everything is ruined. Time shenanigans optional.
-Pac Man 2. Like Pac Land, but this time there's weird 16 bit pac man walking about, players can smack things in the background to interact with 16 bit pac man and make him do dumb **** like in the original game.