I am a really strong advocate of eliminating the final exam. You could take the mid-term exam and extrapolate a grade, or you could take the current average. If students can make the case that their final exam would have raised their grade, then do different math.
If this were an Earthquake with buildings fall around us, would we be having these conversations???
Folks, please get real about this situation. Let's appreciate the great learning that we're been able to accomplish and just get the semester done as quickly as possible.