Wire protocols are already here: WebDriver wire protocol: http://www.w3.org/TR/2013/WD-webdriver-20130117/

Firefox "marionette" automates (controls) firefox via the WebDriver API: https://developer.mozilla.org/en-US/docs/Marionette

Chrome also has an "automation proxy" API that is used by ChromeDriver. http://code.google.com/p/chromedriver/