Are you talking about using an expose clone and creating shortcuts to functions that you can use via the quick launch?
-- You could use one of the expose clones (I.E. DExposeE2/Switcher) and create a shortcut to each of the functions which you could use via quick launch and or another toolbar. http://insentient.net/
Or are you talking about replacing the show desktop button on the bottom right?
-- I don't think this is possible.