A brother from another mother: https://bastillebsd.org/ Bastille manages jails using shell with many of the same constructs you'd find in docker. I like it over other jail management software in BSD because it has so few dependencies.
I'm also quite impressed by cbsd - shttps://www.bsdstore.ru/en/about.html - though that's more of a 'maximum overkill' solution in spite of being a CLI/TUI driven tool.
Currently I'm going through a phase of building and managing jails with just the stuff in FreeBSD base, but that's entirely intended to only be a phase - it'll last until I have the way all of it fits together burned into my brain well enough to be confident debugging it, and then I'll stop banging rocks together and go back to using higher level tools like a sensible person :D
Absolutely, it adds a lot of value for a shell script that is about 100 LoC.
By the way it took me a while to get why it was named Bastille. As La Bastille was a castle built to defend Paris from English attacks during the Hundred Years' War, and then turned into a prison.