I try to get a look at your solution but I have few questions.
First one is about filtering on the firewall.
I see the cs-netfilter-blocker but this one use iptables.
But since debian 10 now they recommend using nftables.
Other question, I see no collecitons about postfix, dovecot or other mails solutions.
It’s my job to go to the documentation and write everything needed (and eventually share it here) or do you have plan to write those tools ?