Story/Adventure Mode

Like SSB Melee and SSB Brawl even SSB4 will probably have its story/adventure mode.
How should it be in your humble opinion?
Well, I have an idea I will explain with this rough graphic:

See? Before the middle of the story (which might be not really in the exact middle) you cannot change what's going to happen. You can just see the story from a different perspective, and learn a part of it. But once all the characters have joined together a lot of paths are open. Still, since different points of view means even different stages for the first half of the story, even once all the characters are united and so are their point of views, you cannot visit back a stage belonging to a path of a character different from the one you have started the game with.
Obviously my hourglass diagram is pretty approsimative. The chars will not meet together all in once but will start by forming small grops and joining the other small groups. Which means that different chars will share some of the stages in the first half. And, in the same manner, even the multiple ends paths will ramificated, rather than straight from the middle of the story.
Clear??