From my relatively small experience (helping just a few friends with nix) I feel the highest improvement / cost would be making it clear for which user stuff is being done when using tooling. This might be obvious when you have some understanding of nix already but results in very very very painful confusions when one is not at that point yet or not careful. Issues like this pop up even on Discourse.
Otherwise I very much support the initiative and promise I’ll contribute to the cause the moment I signed contract for next job (hopefully during the next 7 days)