I think the first step would be for you to hack together a EclipseLink module to test with. This would be copied into the as7/modules/org/eclipse/persistence folder. I have a hack in mind, for the integration classes that I will tell you about when your ready for it. In a few days, I'll add the hack, if you haven't yet.
You might want to start writing some instructions for how to manually create the as7/modules/org/eclipse/persistence folder as I have done for Hibernate 3 (see https://docs.jboss.org/author/display/AS7/JPA+Reference+Guide). Just keep the instructions local until they work.
as7/modules/org/eclipse/persistence/main will contain a module.xml file that species the EclipseLink jars and dependencies on other AS7 modules.
You will want an EclipseLink test that has a persistence.xml with the following property set.
<property name="jboss.as.jpa.providerModule" value="org.eclipse.persistence" />
When you get the EclipseLink module hacked together and a test deploying, we should see an error about the adapter module not being found. I think we will eliminate that error and instead use a simple no-op adapter module (the hack that I mentioned above). The test case could easily be a test case in as7/testsuite/integration/src/test/java/org/jboss/as/testsuite/integration/jpa (see current Hibernate tests under there).