I added some code to VFS that allows you to programmtically create a virtual directory structure composed of any URL, classloader resource, or byte array. The code is here:
https://svn.jboss.org/repos/jbossas/projects/vfs/trunk/src/main/java/org/jboss/virtual/plugins/context/vfs/
Its incorporated into the VFS testsuite as well.
If you want to see it in action, look here:
https://svn.jboss.org/repos/jbossas/trunk/embedded/src/test/java/org/jboss/embedded/test/idetesting/VfsTestCase.java
The two tests in there dynamically define an abstract jar from resources in the classpath and deploy it into an Embedded JBoss runtime. An EJB jar with a persistence unit is defined and deployed.