We have a similar issue where we wanted recurring invoices to be created in OE (monthly). The primary reason for this is to keep all revenue/billing data in one spot (OE).
We have written a system which we will use in-house (getting tested at the moment). It's pretty basic but does the job for us. If you'd like to have a look or discuss, give me a call at 604-282-6000.
Etienne