Well, there's no need for a Balance Board to move your body around. If it actually uses most of the WM+ then there will be a lot of moving in the game. As in, opposed to flicks of your wrists.

About the possibility of an early build, it is VERY likely. Zelda team is known for spending a while messing with the old engine to gather new ideas and then hops right aboard developing a new game while brainstorming. Even if only for idea-enticing, there's probably an early build at EAD with the old TP or a new, unstable engine with a Link waving his arms somewhat likethe player does.

The thing about them is that, not having the usual pressure from publishers, they can simply throw most of their work out the windows and start from scratch. And if Miyamoto's words are any indication, it seems to happen quite often. I wonder why Aonuma's been on the quiet side, though.