First of all I would like to thank @jamielinux or this extremely helpful piece of code he gently shared with us. I was on the same situation that Andrea, and this really helped save my day and still keep the installation updated.
Actually I run Discourse along other sites, and a mail server, in the same VPS. One of the few hiccups I have is that whenever I update Discourse, it replaces /etc/postfix/main.cf . I have been manually reverting that change; would it be possible to avoid this directly into discourse-ansible code?