This is fairly old but I wanted to revisit. We are very interested in getting this capability into the main server code which is to be able to register plugin components as full domain handlers. I'm looking through the code trying to find areas where this would be a problem and so far it seems relatively safe and easy.
I propose to add a marker interface that could be implemented by a plugin which would tell the InternalComponentManager to register the plugin component as a full domain handler rather than subdomain. Then the RoutingTableImpl would be able to send the packet through the routeToComponent logic by calling hasComponentRoute and, if true, sending the packet to the plugin and the plugin would handle it.
This seems fairly trivial to implement but I'm not 100% sure it doesn't have side effects. Would it be possible to get a patch that did this into the main development line?