Speaking of Bosses, I could think about a world where before the boss battle you deafeat the actual character. Like, after defeating it returns bigger and stronger. Example :
- Speaking of The Legend of Zelda bosses, Ganondorf after being Smashed could return as Pig Ganon on the stage, Vaati would be great either playable either boss, but what about both? His Boss Form could be the dark cloud one-eyed thing (and for his Final Smash I would prefer his Mage Form, as the first phase of his Final Battle in The Minish Cap);
- You defeat Bowser, you get permanent Giga Bowser with stamina;
- I'm seeing Medusa playable likely, and after you defeat her she cuts her head off and combats like that (even thought this could bring confusion to the Castlevania Medusa);
- It's Smash, something random could happen and while battling Meta Knight, Haltmann shows up and puts him on the Mecha Armor...
And then obviously there are normal, unique bosses, Eggman is very likely, but I have more :
- As Pokèmon, if we're not getting any Gen 5 representation then just put a Golurk or a Black-Kyurem;
- Metal Face is alright here, what about the Arachno Queen?
- King Bob-Omb to bomb up the party;
- The Draygon, in an interesting underwater battle, even thought Smash characters can't actually swim;
And finally, someone from the Subspace Emissary returns, Tabuu in a new form, Delta-Rayquaza as angry as ever. Galleom and Duom with some reinforced armor, Rid...oh. Some original bosses would be great too.