Let's play a game.
The next Smash game takes a note from PlayStation All-Stars, and the stages are combinations of various Nintendo franchises (and third parties). What stage combinations would you like to see? The first franchise you list will be the stage, and the second will be the invading franchise.
Here's mine:
Super Mario x Zelda
Star Fox x Metroid
Donkey Kong x Sonic
Fatal Frame x Luigi's Mansion
Xenoblade Chronicles x Final Fantasy
Pokémon x Splatoon
Final Fantasy x Fire Emblem
Sonic x Bayonetta
Here are mine:
Pokemon X Final Fantasy: Legendaries like Lugia and Ho-Oh battle Summons like Bahamutt ZERO in the background.
Mario X Sonic: A hybrid between World 1-1 of Super Mario Bros 1 and Green Hill/Emerald Hill/Whatever Green something Zone.
Pokemon X Pikmin: Small Pokemon vs Big Pikmin Predators.
Golden Sun X Final Fantasy: Battle of the summons.
Mario Kart X F-Zero X Diddy Kong Racing: I don't think i need to describe this one.
Kirby X Wario Land: Just because i kinda like off the wall crossovers.
Megaman X x Metroid: Random past Mavericks battling Metroid bosses in the background. IN SPACE.
Street Fighter X Punch Out: I admit i don't have an idea here but im sure something could be done.
Star Fox X Some Namco Bandai shoot em' up like Galaga.
Tetris X Dr. Mario.
If the Metal Gear universe ever returns to Smash, i want Metal Gear X Xenoblade Chronicles X.