I hit upon an idea last night. What if Adventure Mode comes back, but the Adventure Mode stages are simply segments of bigger Smash Run areas?
That way you kill two birds with one stone.
Here's a list of ideas I had....
Smash Run Stage: Mushroom Kingdom
Segments: Mushroom Kingdom, Peach's Castle, Underground, Yoshi's Island and Bowser's Castle
Smash Run Stage: Hyrule
Segments: Hyrule Field, Lost Woods, Lake Hylia, Hyrule Castle, Temple (of Time) and Ganon's Tower
Smash Run Stage: DK Island
Segments: Kongo Jungle, Monkey Mines, Gorilla Glacier, Gankplank Galleon
Smash Run Stage: Dream Land
Segments: Green Greens, Castle Lololo, Bubbly Clouds, Mt. Dedede
Smash Run Stage: Space
Segments: Comet Observatory, Planetoids, Corneria, Brinstar, Garden of Hope
Smash Run Stage: Kanto
Segments: Viridian Forest, Mt. Moon, Saffron City, Seafoam Islands,Indigo Plateau
Smash Run Stage: Town and City
Segments: City Scape, Beach Side, Construction Site, Countryside, Haunted Mansion
Smash Run Stage: Ancient World
Segments: Fortress, Dungeon, War Zone, Lighthouse, Sky World
Smash Run Stage: Guest World
Segments: Green Hill, Shadow Moses, Wily Castle, Pac-Maze, Tournament Arena, Reactor, Cathedral
Phew, so many... Probably too many... XD