Valeu a tentativa, eu já tinha obtido esse link também 
Estou tentando fazer algo parecido com:
<unknown-pk>
<unknown-pk-class>java.lang.Long</unknown-pk-class>
<field-name>id</field-name>
<column-name>coun_id</column-name>
<jdbc-type>INTEGER</jdbc-type>
<sql-type>NUMBER(9)</sql-type>
<auto-increment/>
</unknown-pk>
<entity-command name="bi_counter_sq" class="org.jboss.ejb.plugins.cmp.jdbc.keygen.JDBCOracleCreateCommand">
<attribute name="sequence">bi_counter_sq</attribute>
</entity-command>
Observando o código do JBoss, o erro de NullPointer ocorre no seguinte trecho:
public JDBCCreateCommand createCreateEntityCommand()
throws DeploymentException
{
JDBCCreateCommand cec;
try
{
cec = (JDBCCreateCommand)manager.getMetaData().
getEntityCommand().getCommandClass().newInstance();
cec.init(manager);
}
catch(DeploymentException de)
{
throw de;
}
catch(Exception e)
{
throw new DeploymentException("Couldn't create entity command: ", e);
}
if(log.isDebugEnabled())
log.debug("entity-command: " + manager.getMetaData().getEntityCommand());
return cec;
}
O código para no primeiro catch.
...
13:16:42,616 ERROR [EntityContainer] Starting failed jboss.j2ee:jndiName=entity/
CounterLocal,service=EJB
org.jboss.deployment.DeploymentException: Couldn't create entity command: ; - ne
sted throwable: (java.lang.NullPointerException)
at org.jboss.ejb.plugins.cmp.jdbc.JDBCCommandFactory.createCreateEntityC
ommand(JDBCCommandFactory.java:159)
at org.jboss.ejb.plugins.cmp.jdbc.JDBCStoreManager.startStoreManager(JDB
CStoreManager.java:474)
at org.jboss.ejb.plugins.cmp.jdbc.JDBCStoreManager.start(JDBCStoreManage
...
Aparentemente ele dá nullpointer pq não consegue achar o EntityCommand, ou a própria descrição do entity (…manager.getMetaData()), ou o nome da classe. A classe está no package adequado no arquivo jboss.jar.
Alguém dá mais ?