The needed hack that I mentioned earlier is done and waiting to be merged into the AS7 codebase (https://github.com/jbossas/jboss-as/pull/379).
Once this is merged in, you should be able to sync up with AS7 codebase and the wheels will be a little more greased.
More specifically, when the org.eclipse.persistence.jpa.PersistenceProvider provider classes is used, the org.eclipse.persistence module will be looked up. The org.eclipse.persistence module files (module.xml + jars) are expected to be in as7/modules/org/eclipse/persistence/main. I think your last note mentioned the path without "main", so be sure to correct that.
I created a simple (currently ignored) unit test for TopLink that mostly worked (except TopLink couldn't find the JTA transaction manager which causes a unit test failure). I didn't do the same for EclipseLink. I'm leaving that for you (which you have mostly done).
After you have synced up with the code changes that I mentioned, we can talk next steps (mostly getting your EclipseLink unit test to pass initially). I suspect that getting EclipseLink to know about the AS7 JTA transaction manager will be needed.
I could also point you to my github repo, if your anxious to get the hack sooner (I think that http://community.jboss.org/wiki/HackingOnAS7 probably mentions how we can "git cherry-pick" changes between repos).