It would be nice to have some kind of sales record table. It could show the gross for each sale, followed by an approximate cut taken by the gateway, then shopify’s percentage, then the net income of the sale. Perhaps you could include tax deductions there if the store uses it. Also, in the products DB, the option to add cost prices (hidden from users), so that profit calcuations could be displayed.
I think there’s a great potential for you to add features to help in the business side of things, as well as in sales.