The day I first saw the SSBB video, I thought "man, Dedede would be great for this game. . ."
By the way, I like the third image the best. That just IS Dedede, ya know?
Up-B could be a Hammer Uppercut style attack.
The one where Dedede bullrushes, but falls over later, sounds more like a dash attack.
His Super Smash could be "Hammer of Dreams" or maybe "Illusions." A new move for Dedede, he uses trick magic via Tanuki Leaf, and super jumps off the stage, a little to the side. As he comes down, his hammer, now GIANT sized (huh, I think I got this from Snorlax), comes raining down upon the entire stage. It would have two sweet-spots: one in the exact center of the giant hammer, and another right where Dedede himself is, and where his actual hammer would really be.