Hmm, I think their final Smash should be summoning a mountain onto other players. Or something like that. You know, you grab the Smash Orb, use the correct button, and all of a sudden, a mountain smashes on top of a nearby player. That would be awesome. Not an avalanche, but something more along the lines of Everest. Or at least, Kilimanjaro.
Although, as an after thought, I'd like it if they summoned two 8-bit versions of themselves, and all of a sudden, you'd have four Ice Climbers instead of two. That would rule pretty hard, too.