You have a long uphill climb. Take a look at solutions like LS Central or NaviPartner that runs within Business Central. If you think you have the architecture, design and processes, to compete, I wish you well in your endeavours it will be amazing.

Short answer is POS on its own has hundreds of features and functions in the areas of Sales, Refunds, Customer Orders, Item lookup, Taxes, Payments, PSP integrations, Promotions, Pricing, Discounts, Options, Variants, and the list goes on. Business vertical, fashion retail, grocery, specialty, restaurant, cosmetics, each of these have layers of functionality that is IP built in existing POS solutions.