You're confusing implementation details with semantics here quite a bit, but I think I can puzzle it out: you'd like to be able to create references to an object which don't keep it alive but do stay "valid" in the sense of never being confusable with a reference to any other object even after the object is destroyed. Those references would never be "resurrectable"; they'd just be usable as stable keys in dictionaries and so on. It turns out that we actually have most of the facilities we'd need for this already as part of the implementation of unowned references. How would you expect to use these?
I'm not sure I agree with this assessment.