Good concept but I don't think it sounds good in practice. In actuality, you would need both hands on controller and standing up in front of the camera, thus the shape of your body would be the same, just in different location on one axis. The game also can't count on player to move forward and backward to increase/decrease the size of the shape for the space limitation. So, the best the game can expect is for player to shimmy left and right.

This concept would be better if it only need one hand on controller or controller free, so people would be required to pose specific way for puzzle solving.