It requires an enormous amount of work, otherwise, it will be a mediocre limiting crap similar to Scratch. Scratch-like languages seen in YoYo Game Maker or Construct give no value, because they are just a line-by-line graphic/text representation of real code. JS is already easy to learn and is infinitely deep, so I would not add another language that will be thrown away by a user after two-three weeks of use, but would rather gradually teach a user how to code on js.
If we're talking about a holy grail similar to Unreal Engine's blueprints, a bunch of delicate questions appears. What about modules? What happens if one was removed/added? How to preserve JS flexibility and its prototype-based typing? What about purely JS, not-ct-targeted libraries? And, yeah, it requires even more work to be put into.