Heretic of The Seventh Circle
I think this kind of sets an unreasonable standard for session 0. It will not ever cover every thing that could possibly happen in the game and how the table wants to handle it. And it shouldn't.This, like many topics of this nature, seems like the kind of thing that should be addressed before the first session. It's not like most games have actual mechanics for dismemberment, so it's something the GM should have in mind as a possibility before they even get started, and that shouldn't be a possibility that they should keep to themselves.
This is a topic where clear communication during the course of the game is key, not where we shouldn't expect groups to think ofevery thing that could happen and know (sometimes years) ahead of time how they're going to feel about it and thus how they want it handled if it ever comes up.