I would like a second life-like system, with little big planet "game in a game" style gameplay "gameplay-ception?"
one persistent world where every dev/user makes contributions -similar to gary's mod- like enhanced textures, assets, patches etc, and user in the game can create games with easy to use tools then sell/trade those games with other users...
the world would have many different settings, and if the setting isn't right devs could import it into the main world, so it would be ever growing...
then being the only piece of software running on the google gamebox, it could be highly optimized, so an apu or custom super arm-based soc would run it without the need for extreme hardware...