The FAIme build service now supports packages from the backports repository. When selecting the stable distribution, you can also enable backports packages. The installation image will then use the kernel from backports (currently 4.14) and you can add additional packages by adding /stretch-backports to the package name, e.g. notmuch/stretch-backports.
Now, the FAIme service offers images build with Debian stable, stable with backports and Debian testing. The web page is https://fai-project.org/FAIme If you have any ideas for extensions or any feedback, send an email to FAI.me =at= fai-project.org -- regards Thomas