Rules Integration

I am trying to build my messaging setup entirely based on rules and not in a custom module. Right now I am looking at notifications for advanced forum. I have created subscription flags, created a rule to automatically subscribe node authors and comment authors, created a message type and created a rule to log the message when new content is created in the forum (either a new node or comments on a node).

So far, so good. Now with rules, I can trigger on new content and select an action to send a message with message notify. That does work and sends messages correctly. However, I seem unable to get a true subscription going, these notifications do not use the queue and it does not integrate with other modules such as message_digest.

Is there a way to trigger the subscription functionality through rules?

Thanks, J.