As somebody who has written some "part 1" articles that promised follow-ups, sometimes the negative comments on the first article discouraged me from writing part 2. Useful, constructive feedback can help fix the article and feed into part 2, but kneejerk negativity about something you've done for free is hard to hear. Even more useful would be someone offering to help write part 2.
> ... sometimes the negative comments on the first article discouraged me from writing part 2.
I certainly understand that and I hope I didn't come off sounding ungrateful. A few years ago, I spent a lot of time writing articles and recording videos for my blog and, fortunately, I never had to deal with such negative feedback. I can certainly see how it would discourage you from continuing.
It's simply a bit disappointing sometimes to Google for something, find an article that sounds like exactly what I was looking for, discover it's a "part 1" that didn't quite cover what I needed, then go looking for "part 2" and realize it was never written.
It is also often the cast that best intentions lead one to write part 1 but life gets in the way for part 2. I try to tune out feedback that isn't constructive (like a lot of feedback is these days). I wonder if it is (or could become) a thing to ask the original author if they'd mind someone else taking up a new draft?
You should also tweak your guide for RHEL7 based distros. Things like journald, firewalld etc. Also remember that in RHEL7 sysctl and security.conf are configured a little bit different now.
Red Hat Enterprise Linux 7 Security Guide is a good reference.
Thanks for the very useful article. Minute point: for Rackspace, I thought that ServiceNet is a shared network and you require Cloud Networks to establish a private net.