I'm using a plugin called WooCommerce Additional Variation Images.
I can see from your answer here - https://www.wpintense.com/question/external-wordpress-images-for-product-gallery-2/ - that gallery images can be added external images.
Would this also be the case for additional variation images? (Also using WP All Import)
Currently it handles featured images, thumbnails and gallery images but NOT variations yet.
If this is something you’re keen on, I can add a feature request to get this implemented.
I’ve added this item to the Trello board: https://trello.com/c/3S2dadBD/74-ei-add-ability-to-configure-variation-images-using-ei
Variation images and variation galleries have been implemented