I get that this is a joke, but I do think a really cool concept for a game would be one where there is just an API for the "state" and that is responsible for the mechanics and rules of the game, but that you would build your own custom client for the UI. For example, some kind of spaceship battle game where you create your own interface for controlling the ship... it would be kind of a meta-game where creating the interface a certain way might give you advantages in terms of efficiency versus others.