I agree completely about being conservative. Only reason I think it’s feasible approach is that I believe we can find good format to allow seamless and lossless 2 way conversion between ipynb json and this new format.
To clarify too, reason I’m looking at this change is less about GitHub itself and more about version control in general. Change like that would benefit from every tool for software dev - whether it’s GitHub, GitLab, git itself of Mercurial, that’s why I think it’s worthwhile.
I see this thread Should Jupyter recommend a text-based representation of the notebook? is discussing exactly this idea, so should we move to that thread to avoid duplication?