If you were only looking for a replication of a machine config you have running at the moment, without the ability to add extra packages, then you can create your own ISO.
This post https://www.reddit.com/r/NixOS/comments/y1xo2u/how_to_create_an_iso_with_my_config_files/ has more information.
This seems like a decent alternative in lieu of replicating the entire nix store.
Carve your config in stone! :)
If a solar flare happened that knocked out the internet your computer wouldn't work anymore.
that knock out the internet for months.
This could have ended the discussion.
I think you'd need to clone the entire nixstore or whatever. I made a similar post:
https://www.reddit.com/r/NixOS/comments/12m8ojo/how_big_is_the_nix_store/
So you would need a ton of disk space, atleast 200TBs
Search for "Carrington Event" in 1859. Were such a coronal mass ejection event to re-occur in modern days; it would be beyond catastrophic. The problem is not so much a loss of Internet as a loss of electrical power that could last decades. It would definitely fry any exposed electronics, especially semi-conductors. It would destroy power station transformers which are not easy to manufacture and would take many years to replace a large number of them. Providing you had power to run manufacturing.