We would like to be able to offer a limited number of gift vouchers, of varying values, to our customers, and are looking for the best way to do this.  We have looked at Coupons and Gift Certificates, but neither seem to fit the bill perfectly.

Coupons:

If we set up a coupon at a flat rate and give the customer the code for it, what then happens if their next order does not come up to the value of that coupon?  Presumably there’s no way for them to claim the remainder of it next time?  If on the other hand we set it at 100%, they could obviously order way over the coupon total.

Gift Certificates:

These rely on the use of credit notes, and Commerce does not allow for the use of credit against new orders; we use and online payment gateway, and the customer would have no option other than to pay up front and await a refund being issued.

Am I missing a better way?

Thanks