Yeah, it would be fairly difficult to build, which is why getting feedback would be useful, but there's a catch 22; people who already know what Org is are fairly comfortable using Emacs and I don't know how to find out if people not that found of Emacs itself would still find Org useful, or if combining apps like Ulysses and Omni Outliner is good enough for them - the worst part is that because they don't use Emacs, they can't tell me.
This really may be the 'just build it and see' sort of scenario.
I've often about some sort of app that uses Org as a design basis, but stores data in a way that makes it easy to access remotely without having an Org parser, to be easy to sync and query programmatically, and is designed for the modern world in terms of connectivity and interface.
I think that could absolutely kill it.
Imagine writing extensions in js or lua or whatever, and having those extensions have clear DOM-like access to the outline, have full access to their stdlib, have access to built in services like notifications, etc.
Imagine being able to programmatically access and manipulate the outline from wherever: webhook to add an outline node from IFTTT, twilio access your notes? etc. Yes you _could_ do that with Emacs, but IMHO it would take an incredible amount of work to not suck, partly because all the various pieces necessary feel like hacks on top of hacks.
Sort of how Atom and VSCode provide _much_ better interfaces (both code and UI) to your source code, and are starting to make honest inroads against the established players (like Emacs and Vim).
I've been wondering about this, as well, and so have been working on an Emacs configuration that makes Emacs work as close as possible to a "normal" text editor (hopefully allowing learning org-mode without the barrier to entry of Emacs itself):
This really may be the 'just build it and see' sort of scenario.