While .attrs.sh is bash-compatible, the declared attributes are different than what existed. E.g., the output $out is now ${outputs["out"]}. I suppose for compatibility we should ensure the original variables still function.

Feel free to steal from: https://github.com/mayflower/nixpkgs/tree/structured-attrs

oh, nice! It certainly seems there is still a lot of work required. Is Mayflower going with this any further?

I don't have time to progress further for now. Building stdenv partly suceeds to build in my branch, in the sense that as far as I can see the only problem is that I have a problem with input ordering or similar so that the bootstrap tools are referenced instead of stuff built during stdenv bootstrapping. but didn't manage to debug that further until now.

I know @matthewbauer, @Ericson2314 and @edolstra at least were interested in this too.

Furthermore I'd propose pushing my branch to NixOS/nixpkgs and create a follow-up PR so that a larger number of people can work on this concurrently? Feel free to just go ahead and do so if you think that should be the way to move forward on this.