Actually, as I specified before, in a controlled environment, it makes it easy to help people not log in with unapproved clients. IE, sure you can hack things to get in, but if you download some client that your IT doesn't want people using, and it fails to connect, that's an easy way for the employee to go "oh yeah I'm not allowed to use this" instead of being let in and using something and then later being told "you weren't supposed to be using that". Clearly it's possible to circumvent it, but it does provide a good reminder.
I was going to suggest adding Coccinella to the list, but at this point you've confused people who might read your article and go hacking Coccinella to pretend it's Psi. Effectively the entire plugin is "suggestions", not enforcements. If you feel like writing client certificate support, be our guest. And hey, if people want to hide the fact that they're using Coccinella and instead announce to the world that they're using Psi, then more ++usage stats for Psi it is!