Even with external references you must specify
the home and remote interface class name in <ejb-ref> tag of ejb-xml.jar.
It's not what we want to do.
We want full "hot deploy", "dynamic" ejb calls from
an other ejb.
We do not know the full EJB class names of the EJB that will be accessed by our EJB "A". We only know their JNDI names at runtime.