Featured images from outside the media library

I am using WP multisites and am developing a process where I will be cloning sites with large catalogs of products. What I would love to have happen would be for the featured images for all of the products I create come from an external source. This way I can save resources and better facilitate image updates as needed.

I am beginning to think something like this is not possible because it seems that featured images MUST exist in the media library for the same site. I’d love any suggestions though.

Thanks.