For today, we have a mech game.
Players wll be in control of large mechanized vehicles. Some of them bipedal, quadrapedal(word?), and wheel based. This will be a Natal only game. Players will control the vehicle via a virtual cockpit that is 1:1 with their surroundings. Depending on the vehicle, different cockpits will be available to control the vehicle. I will us a bidepal mech as an example. Players will use their hands and feet to interact with a virtual cockpit. Turn the vehicle on by using a series of buttons. Accellerate by pushing a lever forward. Etc. Fire various weapons using buttons in the cockpit. It would need to be a more slow paced game with less emphasis on twitch gameplay and more emphasis on immersion and strategy. It could be played online. You could perhaps have two players, a driver and a gunner. Use the RGB camera to be able to have small video screens in the cockpit that displays when they are talking. Voice commands could be used to send team mates orders or provide them with visual strategic insight.
The on screen visuals will need to have an indication of where your real world arm and possible feet positions are. If a joystick is a little to the right and forward, you would need an on screen visual showing where your virtual arm is located so that you gain an understanding of how to interact. Once a player is used to this, it would become more easy to just "know" how far that button is, or how to use that lever.