The main issue is that an OS can't clone itself. It needs something outside of it to clone it.
Right but that is not done itself. In your example it was presumably a human connecting the console, booting to single user mode, etc. Unless you tell me how to put that in cron, it is still not itself.
OTOH the IP did ask for a single image copy at some single point in time and not for anything automated. So with my command summary it is perfectly possible to generate an image that can be put back on e.g. a new SSD in a very similar fashion.
Isnt it faster to reinstall OPNsense completly (done in 5 Minutes) and import the config Backup?