I feel like brackets’ inline-editors are incredibly powerful, is anyone working or thinking about adding this to Atom as a package? Would it require modifications to the editor core?
That depends on how you want to display it. If it appears in another pane or in a pop-up that would be easy, and in my opinion just as useful. If you want it to appear truly inline, pushing the real lines apart, then it would require changing some basic functionality of the editor display.
I happened to overhear an atom team member discussing this very change with a user at codeconf. I wouldn’t count on it happening anytime soon though, or ever.
An idea. One could insert the inline text in the real text and color it to look like brackets. The trick would be to make sure it is adjusted when the real text changes. That could be done in a regular package with the existing API.