Trigger task creation when event state changed

Event schedulers sometimes work on events very far out and even reserve their multi-million dollar facilities up to five years before the actual event. So they need to create an event and reserve a space, but they don't want to send the notifications until the event is confirmed. They would therefore like to have notification policies tied to event state and re-notifications also tied to state. From what I gather, it might work if the notification policy asked you to choose which state would trigger the notification and also ask if you want notifications cancelled if the event state is demoted. In their case, Tentative wouldn't trigger, but Confirmed or Sealed would. Moving it back to Tentative would cancel the notifications. They would, of course, want the notifications resent if the event was reConfirmed or reSealed. I don't know whether it would be necessary to have these options in the notification policies, or if they could be system definitions.