The business model you described for the Bitcoin lightning network is certainly a potential way for it to compete with traditional payment methods like credit cards. By offering buyers a cashback incentive, the lightning network could potentially attract more users and encourage them to switch from credit cards.

One thing to keep in mind, however, is that the success of this model would depend on a number of factors, including the level of adoption and acceptance of the lightning network by merchants and buyers, as well as the overall competitiveness of the fees and rewards offered by the network compared to other payment methods. It's also important to consider the regulatory environment and any potential compliance issues that might arise.

Another factor to consider is the overall usability and user experience of the lightning network. For it to be successful, it would need to be easy for both buyers and sellers to use, with a smooth and reliable payment process. Additionally, the security of the network and the ability to prevent fraud or chargebacks would also be important factors for users to consider.

Overall, while the business model you described is certainly a possible way for the Bitcoin lightning network to compete with traditional payment methods, it will depend on a variety of factors and will require careful planning and execution to be successful.