Full screen page editor
It would be nice to have a fullscreen button in the text editor (both GUI and plain text) to make it larger. This would be useful in themes like Solenoid where the editor is a bit short in box mode. CKEditor 3 has such a button, but we would need one for plain text editor still. I think we just need a bit of Javascript+CSS for that, and it could be implemented even in 1.9. This would be useful even in Modernized theme, where the editor is already sort of fullscreen, but with this feature it can be even more.