Prestashop Custom Module - Multi File Upload from product page, set options, save options and files to cart, files downloadable in Back Office

Dear developers, the project is an fairly simple online-shop for a local print service selling customizable print products. I need experienses with file handling, order proceeding and backoffice compatibilty in prestashop. What my customer needs is file upload form for the product pages. The file upload should be: massupload (multi file). Each uploaded item shoud then (depending of the file type) contain a preview image and a quantity field that influences the price and the "all-togehter-product-quantity". For an overview and for details about file handling I put together a little draft which you will find in attachment. If my ideas of the file-handling are too complicated, one could change and simplify this step. Important is that the store owner can easily distinguish: - which files belong to which order - which files belong to which product of the same order - which file has to be printed how many times - files of one product should be easy to download in one step I look forward to your responses. If you have further questions, let me know.