We're looking to create a new Shopify app.
1. The app will need to add custom field to the checkout page under the shipping address.
2. If the customer fills in the field, the value would appear in the order details section.
3. The customer should also be able to add/edit this field when editing their stored addresses.
We've done a bit of research and we're not sure if the above is possible. If it is we're happy and have a good budget to pay someone to build the whole app for us but we will need you to show us that you can do it.
Please email me with a rough quote to build this for us and a brief explanation of why you believe it's possible: email@example.com
Checkout page can't be customized but we have feasibility with cart page so let me know if that would solve your requirement or let communicate over firstname.lastname@example.org to bring out some solution.