What about taking an approach like Tomcat does with respect to embedded context.xml files in a WAR;
When the EAR is deployed, have a meta deployer first scan the archive and copy any "service files" (-ds.xml, -hornetq-jms.xml, etc) encountered to the location expected by AS 7. Then proceed with the deployment as it normally would be done.
If the meta deployer uses both META-INF and jboss-app.xml or a simular file to discover the embedded service files, then everything that worked on AS 6 and before should continue to work on AS 7.