This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
I think you can configure navigation not only through face-config.xml, but also you can use the FacesContext.getCurrentInstance().getApplication().getNavigationHangler()... this will give you the current NavigationHandler object. Using this object, you can play with the navigation. (Please refer to the jsf docs as the above sequence may not be the right one).
Please hollar if you got better solutions... Gud luck !