It seems like this is not easily possible. Some packages names have changed from Hibernate 4.2 (which is bundled in JBoss AS 7.5) and newer versions (Hibernate 4.3 and up). As the JBoss JPA module for Hibernate has package names hard coded, it cannot initialize hibernate properly. I tried to write some wrapper classes to work around the changes in package names, but ran into other incompatibilities further down.
In the end I ported the Hibernate 5 Feature that I needed back to Hibernate 4.2 and integrated that into JBoss.
Why not take EAP7 beta which has .GA coming out shortly.
or just take WildFly 10 that has all you need already integrated?
Unfortunately, I'm dealing with a legacy project that uses EJB2 entity beans - so Wildfly is out of the question because of the lack of support for these. EAP7 might be an option if it does suppord EJB2 entity beans.
The solution I ended up with was to backport the bug fixes I needed from Hibernate 5.0.9 to Hibernate 4.2.18 and using this patched version instead of the bundled version. I did not succeed in replacing the bundled version of Hibernate with a newer version.