I posted the "answer" because you seemed like the kind of person who thinks perfect is the enemy of good. While it's possible that the suggested automatic update will completely hose something (hence the "not a good idea"), you seem to be willing to take that chance, and if you get cron's email, it will show you if it blows up and what it did to blow it up so you know how to fix it.
A slight upgrade (but major programming change) to this program might email you the packages needed to be upgraded and an "unlock key" you would post on a master server somewhere to authorize the program to actually perform the upgrade which it would check on the server for next time the program is run, making the install automatic but not the decision to do the install.
A "more correct" answer would be some kind of system that determines the update flow, detects when additional packages get roped in, maybe checks semver on the packages, and detects a potential for major disruption, but that's way more complicated than Debian's solution. I figured if you were good with how they updated things, then you were good with whatever packages are offered as an "upgrade" in FreeBSD.
Sometimes, though, upgrades will bring in dependencies and cause breakages. That's why people think you should use a CI/CD (more infrastructure intensive) to detect this or just do it manually (more labor intensive). I sometimes YOLO
pkg upgrade
on things I'm not sure about, so why can't you?