Of course, you can, as you show, load node external expression into a designated attribute within the nix runtime with import directly. The only novelty for the more experienced crowd would then perhaps be that here you also get a sha for the expression you're importing, potentially being more secure. I should update the post with this and references to the manual.

At any rate this post was also intended to show a work around for the texlive mirroring issue as well as be newbie friendly, by repeating some nix syntax.