I am developing a Shopify checkout UI extension. Using the extension, I want to create a custom checkbox, with my own text and styling. I would use the settings on my store to hide the built-in Shopify checkbox on the checkout page, that lets users sign up for email marketing. Then, the checkout ui extension would provide my custom checkbox, which would tell the user they could sign up for marketing. If that is clicked, my own app would handle signing up the user for marketing in the backend.
The reason I want to do this is so I can complete additional actions when a user signs up for marketing on the checkout UI. The built-in checkbox doesn't allow you to verify whether they user has checked it or not.
Is this viable for a Shopify app? It works fine locally, but I am worried it might violate some policies or best practices on privacy and customer data.
If no checkout functionality is being removed or altered then expanding how the marketing opt-in option operates should be permitted. In in mind however this will be reviewed by the app review team to ensure it's set up correctly.