Save the ifplugd.sh script and hostname in the backup as well. I have a usecase where these two files were modified.
Additional applications might store files in /etc/default and it is the easiest to backup up all of them. This has the danger that after an upgrade the default file is not compatible/optimal but we will need to deal with that once it occurs.
Create shell scripts that backup and restore configuration files used by the sysmocom products.