I agree- there could be an option to check first "extenuating circumstances", then"natural disaster", "area wide power outage", "death in the family" and so on, with then a text box to briefly explain- "Hurricane Florence", etc. when having to cancel. For personal extenuating circumstances, like medical issues, a death, or access to your property being blocked because of a burst sewer line or something, there could be a place to attach documentation.
If there is any doubt on Airbnb's part as to the validity of the extenuating circumstance cancellation, they could contact the host for further documentation, but in the case of a natural disaster, it's a no-brainer for them to check out. The cancellation should automatically carry no host penalties, nor require the host to phone first.
There are natural disasters all over the world at any given time, some confined to very small areas, so I don't think we can expect Airbnb to keep track of all of them, but these options would at least not make the cancellation process for such things so time-consuming.