Direct File Upload on Product Detail Page (PDP) for Promotional Products and Similar

We would like to offer users the ability to upload artwork or supporting files directly on the Product Detail Page (PDP), with that file information carried through to the basket, rather than requiring the upload to be done at the basket stage. Ideally, the uploaded file would appear in the basket as a clickable attachment with a preview link, allowing users to view what has been uploaded - similar to the behaviour seen with Vpress configurable products. We would like this functionality to be separate from the line reference field, as that field is useful for other purposes.

This would be especially useful for promotional products, where customers often like to send their artwork to us when selecting the product.