I'm not familiar with FocusPanel, but it looks like it's used by a variety of subclasses that need to accept keyboard input for various reasons. So I don't think this is a good idea in all cases. Perhaps FocusPanel needs a way to set the ARIA role and you should do this only for your app?
http://gwt-code-reviews.appspot.com/1803804/ -- http://groups.google.com/group/Google-Web-Toolkit-Contributors