This is a great idea. Let Costello or Danger Mouse produce the album and have other singers sing some new songs of his. Just a one-off experiment. I wouldn't want him to try to write a song for a specific song for a specific artist though. Name and Address was just written in Elvis style. I would like the producer to pick who sang what without Paul trying to write with any one specifically in mind.
What's weird is that, in the future, there may be software that lets a person write a song and have Paul sing it because they will have captured enough of his words and vocal sound waves where they can transfer any word he sang into any notes you want. I don't think that is out of the question.