2. Score reaches threshold, shopper is first denied any coupons (this takes a slight change in rules).
How is this going to increase revenue and profits? You're essentially telling customers that you don't want to do business with them. That will probably cause greater damage to profits than coupon fraud. For most vendors, it would be better to detect fraudulent coupons and reject them on a one-by-one basis, even if some percentage of fake coupons get through.