I've seen the kind of animation you did, but this doesn't suit what a collision animation should be. Smash bros is a 2D-move game, and the type of colission for it is always 2D. This means you can't make it rotate as easily, as the colission is not a disc, just like the platform, but a square which will come to be a single segment when you rotate it 90º
A good animation for this could be make it go up-down, or rotate it in the z axis, to make it balance. But I don't think the rotation you did is so easy to implement. Maybe it's possible to make, but not just attaching the colission to that object, something complex should be thought
Anyway, I'll attach the colission to one of it's bones and you try to make it work best
EDIT: Done, but untested (not at home right now), so I don't know what it will do O.o
http://www.mediafire.com/download.php?nzrhfmjd2j1
I've figured out a way to make the rotation thing to work, maybe when at home I try it