general issues aside, for me one of the issues with emacs is that for historical reasons there is a cut between elisp and C that's really high up and pretty ragged. ideally a large composable lisp project like emacs would have a very accessible continuum between the surface and the underpinnings.

so I don't think one can achieve that by maintaining 100% compatibility. a much smaller base system build with better semantics that was notionally compatible would be something I would be really excited to contribute to.