I've created a new FAI version. This version replaces two big packages in /etc/fai/NFSROOT with smaller replacements. emacs25-nox is replaced by zile and dnsutils is replaced by udns-utils. This will save more than 100MB in the nfsroot.
FAI 5.8.2~bpo9+2 is now available for stretch in the fai-project.org repository and will include default configs for a stretch nfsroot. FAI 5.8.2 was uploaded to unstable and includes config for creating a buster nfsroot. This version will become available in the fai-project.org repository for buster during the next days. -- regards Thomas