[feat proposal] Propagate channels to parts of configuraion (modules, systems, etc.)?

It seems like a good idea to be able to access distinct channels in e.g. modules. Let's say we want some module to work with specific version of pkgs regardless of the system it's being evaluated for. What I have to do now is

let
  pkgs' = inputs.specific-nixpkgs-version.legacyPackages.${system}.pkgs;
in
... # use pkgs'

I feel it's just redundant work since we already declare different channels in our flake. And it'll be worse if we want some specific overlays inside the channel.

Maybe it's a silly request and it will break something if implemented straightforwardly. Or maybe it's already implemented and I'm blind. Your thoughts?