In this case copy-paste makes sense, but making step-by-step guide describing each part of generator helps a lot understanding how everything works. Look that changes in existing repositories are much easier if you have some experience in production. Therefore I would not recommend it for new developers. 
Somebody may not agree with me and they may have a solid arguments for it, but I’m used to think in long term. What would happen if new developers would “learn” to copy-paste existing code and only slightly modify it for their needs. Do you have a red light already? No? What about I would mention AI-based generators? 
Also there is one part missing. It would be worth mentioning how to publish said archive to hex server. 
That’s said … In general I did not heard about many Elixir generators and writing the article about it is amazing idea! 