What problem does this address?

Right now you can tie the cover block's image to the featured image, but that's as dynamic as you can get. Cover blocks make great containers for synced patterns and it would be great to be able to have block overrides on the cover block's image. The controls are already in the block toolbar, so it shouldn't require too much UI adjustment.

What is your proposed solution?

Enable block bindings/overrides on the cover block's image ID attribute.