Hi @LittleWho,
As you can imagine you won't be able to get that behavior out-of-the-box.
I guess I'll start checking the Magento\Catalog\Block\Product\ImageBuilder class (I guess) to change the source of the image.
I didn't tried with M2 yet but with M1 I've worked on the Image helper to do something similar.
The idea here should be to replace the exact moment when the URL is created.