Good question, and something I did actually start writing about in my original post but worried it was diluting the point. I think it would need to sync seamlessly with GitHub so issues referenced in commit messages link the commit to the issue - possibly even two way sync with GitHub issues - for it to still be usable and useful for the dev team.
But, GitHub has really only sown up the issues part for developers, for everyone else it's a mess - so if your differentiator is building something that's useful to everyone _else_ on the project, you could be on to a winner. On our projects, the everyone else typically outnumber the developers by about 3 to 1, sometimes even more. These are designers, project managers, client-side stakeholders etc. All of these people need to interact with an issue system, all of them need to be able to track progress, all of them need visibility on how a project is going.
Jira will tell you that that's what they do, but of course it isn't, Jira is a crime against humanity.