The existing Brewfile functionality what Nix-Darwin's Homebrew module currently uses behind the scenes, so any improvements here might also benefit some Nix users on macOS (including me!).

The conditionals and cross-platform stuff might also make it possible to write a single module here that enables use of Homebrew as an escape hatch both on macOS and Linux/NixOS, which would maybe be kinda cool.

So thank you for that work. :)