I don't see how this is different from setting the needsClientAuth property directly in the DomainServerSocketFactory:

<mbean code="org.jboss.invocation.jrmp.server.JRMPInvoker"
   name="jboss:service=invoker,type=jrmp,socketType=SSLSocketFactory,wantsClientAuth=true">
   <attribute name="RMIObjectPort">0</attribute>
   <attribute name="RMIClientSocketFactory">org.jboss.security.ssl.RMISSLClientSocketFactory
   </attribute>
   <attribute name="RMIServerSocketFactoryBean"
      attributeClass="org.jboss.security.ssl.RMISSLServerSocketFactory"
      serialDataType="javaBean">
     <property name="bindAddress">${jboss.bind.address}</property>
     <property name="securityDomain">java:/jaas/rmi-ssl</property>
     <property name="needsClientAuth">true</property>
     <property name="CiperSuites">TLS_DHE_DSS_WITH_AES_128_CBC_SHA</property>
     <property name="Protocols">SSLv2Hello,SSLv3,TLSv1</property>
   </attribute>
</mbean>

The needsClientAuth property is used when creating the SSLServerSocket to indicate that client authentication is required. If the client doesn't provide credentials, the SSL negotiation will fail.

There is also the wantsClientAuth property that can be used to indicate that client authentication will be requested during the negotiation phase. In this case, however, if the client doesn't provide the credentials, the SSL negotiation will continue.

Note: in the JRMPInvoker sample above we are using the RMISSLServerSocketFactory. It implements the RMIServerSocketFactory interface and delegates all methods to the DomainServerSocketFactory. So setting the needsClientAuth property there will end up setting the same property in DomainServerSocketFactory.