Write a paper based on forthcoming chapter in a book
The main issues here are that you can't self-plagiarize, and you most likely need to convince the referees and editors that there is sufficient "novel" content to justify publication. If there is enough new material in the paper, you should be able to prove this. If you feel yourself "stretching" the arguments too much, then it's probably not such a good idea.

An alternative would be to write the paper as a "successor," rather than as an "expansion."