At least in Canada I’d need to know that my system can handle a week of -30 or -40C in my city. Some places are even colder, for longer at a time.
I guess the only remaining concern is that winter storms cause both cold weather and trees falling onto powerlines. The latter is rare though
There are people who genuinely live in the middle of nowhere, on an otherwise uninhabited island as caretaker, deep in the forest manning a fire watch tower, Antarctic research base, that sort o thing, who do need have more options, because if they run out of options they're dead. If you're in that situation you still don't necessarily want gas heating though, a fossil fuel powered generator might make a lot of sense, maybe even more than one, because again electricity is so versatile.
It's much simpler to obtain and fuel a small generator to power meta loads like thermostats/circulators/blowers than a large generator that supplies the thermal load. Fully committing to a heat pump as your only heating would likely involve a large gas generator fed by municipal gas or at least a large buried propane tank (for capacity and temperature).
The straightforward backup heat answer is wood. It's easy to obtain and store, and the primary drawback of it requiring labor and attention isn't a big deal during an outage. Although if you don't do it regularly and make sure your stove is in good order, lighting a fire during an emergency situation might not be the best idea.
I heard about a guy who had copper piping with water flow going around his chimney (on the inside) and then through the house.
That'd be a cool system if you could switch out the heat source, electric and an indoor-safe wood stove. Just get a CO monitor!
They do require power to run (automated dampers, blower, circulators), so I have a small backup generator as per my last comment. And they've gotten a bit expensive (especially now that the US federal tax credit has gone away), but my estimated payback period is around 6 years.
You might wonder why I'm posting in a thread about heat pumps when I just got a different major heating source, but I see heat pumps and wood as two very complementary heat sources. Down the line I'm planning to add a water-to-water or air-to-water heat pump for the shoulder seasons (and summer DHW), so that I don't have to tend a fire (or burn oil) when the heating load is low. One four or five ton unit should take care of my heat loss most of the time, and I won't have to oversize the system to handle the dead of winter cold snaps.