I can tell you that it's possible to use the "depends" attribute to make MBeans dependent on other MBeans, which can delay their creating and starting, so you may be able to push back the starting of the Remoting connector that supports the EJB3 subsystem. Take a look at the "jboss.remoting:type=Connector,name=DefaultEjb3Connector,handler=ejb3" MBean in $JBOSS_HOME/server/$CONFIG/deploy/ejb3.deployer/META-INF/jboss-service.xml. Also, look at the AS documentation. Try, for example, "JBoss Application Server 4.2.2" at http://labs.jboss.com/file-access/default/members/jbossas/freezone/docs/Server_Configuration_Guide/4/html/index.html .
However, the details of your question, which concerns services in the Application Server, is outside the scope of Remoting. I'm going to suggest that you post the question to the Application Server forum "Installation, Configuration & Deployment": http://community.jboss.org/en/jbossas/config .