Sorry, but I don’t thing I understand the explanation. ACF file fields hold the ID of a file uploaded through WP that live is the media library of the site. Without the WP post ID of the attachment and acf file field can do nothing with the file.
It could be that you’re trying to use ACF for something where some other alternative might be a better choice. But like I said, I don’t really understand what you’re trying to achieve.
