Ability to change the focal point is a long asked-for feature, great news that something happens in that direction! Would be nice to have that not just for cover images.

However Ted Magwell is right, it might lead to serving unnecessarily huge image files. So it would be a good idea to implement some suggestions to rather crop the original image if only just 50% (or so) of that will be displayed at the end-user.

Would be even better to actually initialize WP’s image editor screen with a suggested cropping frame that is about 20% larger than the picture that will get rendered for the end-user. That way there is no need to serve vastly larger images than needed, but there would still remain some cropping flexibility for later or for parallax purposes.