I think it’s fine to take a special path to teaching Rails based on your teaching style and your students. You can skip CoffeeScript or anything else that helps accomplish that. All good.
(BTW, this mailing list is for discussing the development of the framework, not its use or teaching. Please use rubyonrails-talk going forward for similar topics. Thanks!)
Personally I wouldn’t mind it if there were simply a --bare-bones flag that generated new apps without any gems whatsoever (except of course the Rails gem itself), as well, without all those comments I don’t need in my Gemfile.