My understanding is that the major difference between a real traceback object and a TracebackException object is that the latter is specialized for printing, so it can be lighter weight (no pinning of frame objects in memory), but loses some utility (can't do post-mortem debugging).

If that's right, then that's definitely not a solution, because trio and jinja2 and import errors all need to support post-mortem debugging.

I'm not against the idea of defining a traceback protocol, but it seems like a lot of work when the existing traceback objects are already perfectly good container objects that are just missing a few simple features.