Enrolment

Here's the envisioned scenario...an annual subscription based Moodle installation which would be universally (all Courses) available to all subscribers upon payment. I'm trying to avoid students having to deal with Enrolling in each Course they want to use (although this will be my fallback position should an easily automated universal Enrollment not be viable). This particular Moodle site would consist of totally static Courses and content; i.e. no subscribers will be creating anything new. As such, the external database Enrollment method seemed like a suitable candidate method. I could index each user id against every course id upon successful subscription. I see there are a number of payment system plug-ins, but my question is how have others setup things up so that successful payment also results in automatic Enrollment in ALL Courses? If no one's done this, can anyone suggest the most efficient approach to achieving this?