I fully agree with Henk,
In my group, we use staging for differenct phases or location of our deployment. We have different DS, JMS configuration for development, beta and test mode, in addtion, our group is relatively small but station in diferent part of the world, we have an central database server, but everyone has a local minimal database which is more efficient to do everyday work, in this situation, we have "central" and "local" mode. We maitain these definition files in EAR, We just need to launch Jboss with the staging parameter for different purpose, It's one of the fancinating part we feel about deploymen in JBoss AS. So I hope JBoss AS 7 can support it as well.