I've always thought Cashu would be a good platform for discount coupons or vouchers.

This is a good thought. I used to do contract work for a company that "insured" gift cards and then the more sexy offer was insuring hole-in-one contests and the like. I think single mint Chaumian schemes lend themselves to these types of uses. On the other hand, it concerns me greatly that they are being masqueraded around as some sort of sovereignty tech. People are easy to trick and they lose vouchers and there's money to be made there. Some ways are a little less diabolical than others.