Speaking from the sidelines: the currently active emacs-devel community has a dearth of people with the right combination of time, access, and interest to guide big changes to macOS support. If you are interested in working on such an idea, I'll suggest just pick up the effort and push it forward yourself, then share it with emacs via the bug-tracker (for better centralized tracking). If you get a patch that seems to work but needs broader testing, posting to emacs-devel can be effective, and if it's not, we/it can help spread the word. Keep in mind that code included in GNU Emacs will eventually need copyright assignment for non-trivial contributions.

It's also theoretically possible to get help from the community that uses the other widely available macOS port (search for "carbon port versus cocoa port" if you want more history here), but, last I checked (admittedly, quite a while back) the mac port used some significantly different internal machinery around select that _I would guess_ has a big impact in this area, and is effectively not directly compatible -- but might still have valuable insights & experience to share.

If you need a *place* to work on this project, ask again here or in the big-tracker, and probably something can be worked out.

I hope that helps! (I stopped using macOS myself several years ago, so I can't offer more direct assistance).

~Chad