Have a look at the URLDeploymentService defined in the conf/jboss-service.xml That will allow you to define external locations for your archives.
The run.bat (run.sh) command has the C option. I tried it and it seems to work ok. So if you have 2 jars, add the following to the run command:
-C "file1.jar" -C "file2.jar"
This is not documented.