I was not suggesting that we record everything copyright on the Work, I also think most of the time the Edition is the right place to record this, especially if copying that information from the copyright page of said edition.
I was proposing that we could also have the ability to add copyright information on the Work if it cannot be completely recorded in an Edition or succession of Editions.
As an example, I have here a book (We by Yevgeny Zamyatin) stating on the copyright page that the translator (Clarence Brown) owns the copyright for the translation and introduction.
I suggest that to enter this I could create a new Work for the introduction with the relationship “Clarence Brown owns the copyright to Introduction to We”
The page even provides the copyright history of the original english translation from the first publication, which again I would have a hard time capturing on an Edition.