Great article and a cool way to learn more about the inner workings of OpenBSD, thanks for sharing. I like the idea of a separate /var/syspatch directory. I typically make separate /var/log and /var/www directories too.

I noticed you're using a good quality SD card and wrote a couple times about flash wear, is there any reason you didn't opt for an mSATA SSD? It might be more resilient than SD.