I manage a store with tens of thousands of "stock" products, which also includes a custom product option. The process of creating a custom product is managed outside of Shopify.
Currently, when a custom product is created by a visitor (on the external web site) the customer's specifications (text fields, location, size, and various other options) are stored in a table - along with the customer's contact information. The visitor is then automatically linked to a generic product page that matches the most basic of these parameters, so that the visitor can purchase it (at the correct price, depending on some of those parameters) and check out. For many obvious reasons, this procedure is fraught with errors.
We would like to be able to pass allparameters (beyond what is possible with variants) collected by the external site so that these parameters are preserved and displayed throughout the process in the product page, shopping cart, and the order fulfillment pages. This will allow our staff to accurately create each custom product.
This appears to be an advanced request and will require a fair amount of modifications to the store and cart. We are not opposed to hiring a contractor who is experienced in this type of customization.