Maybe I'm missing something here but couldn't you just track the whole VM setup (dependencies, dev tools, telemetry and everything) in your monorepo? That is, the VM config would get pulled from master just like everything else, and then the developer would use something like nixos-shell[0] to quickly fire up a VM based on that config that they pulled.
[0]: https://github.com/Mic92/nixos-shell (not to be confused with nix-shell)