But Fair Use is an exemption from copyright enforcement- it is not a transfer of rights. There is no conceivable reading of Fair Use that allows an image user to then broker permissions for other users. Journal X cannot license my work away from me without my say so. They do not have standing to apply a CC license to my work.
The solution should be easy enough. Journal X could exempt contributed images from their blanket CC-license, and they should ensure the images are not atomized and separated from the rest of the paper. The Fair Use of images depends on their context within the publication, anyway.