Attached is Julien's patch and from the mailing list (http://www.nabble.com/Feature-proposal-tf4445574.html):
"I am currently using cargo to write unit tests for JBoss Portal and I
need a feature that allow to augment the classpath shared by all
applications in a container.
I tried first to use the extra classpath feature but it does not
satisfy me as it load the classes in the System class loader and
those classes should be able to see some of the application server
internal classes for my needs since I am developing an SPI library
with different implementations for different application servers.
For tomcat it is equivalent as adding libraries in the lib directory.
It is equivalent to augment what Tomcat calls the "Common"
classloader (see http://tomcat.apache.org/tomcat-6.0-doc/class-loader-
For JBoss it is equivalent as adding libraries in the lib or deploy
I developed the solution for the tomcat 5 and JBoss 4.2 installed