Yes, the worker list is statically defined. However, if you also use a status worker, apache will periodically (default once per minute) check the workers.properties file and load any updates. So, when you deploy a new node you can update workers.properties.
As i understand after reading through the status worker documentation, a capability exists to change the worker.properties manually and reload the configuration without starting the server using the status worker.
But this is totally against the philosphy of Auto-discovery feature available in JBoss, i mean if the application server instances can automatically discover nodes and dynamically converge as part of single cluster, the same should be achievable through the plug-in instead of a manual intervention requirement.
Kindly correct me if i am wrong.