In general subscriptions allow for notification for lots of events - create new, edit, check out, new state, etc., etc. - the way that users are associated with these varies highly. So, this makes it very difficult for the system to provide this.
About the only additional thing that can be done is to create reports for subscriptions for certain events that include the user, using the USER type and appropriate join. Doesn't really solve the problem that you post though.
