I am going to ask a question that I’m a little scared to ask because I suspect it’s really dumb, but here goes: is it at all feasible or practical to have a way to jettison a runaway battery from the aircraft? I guess most of the time the problems happen because nobody knows there’s a problem before it’s gotten too out of control for that.
it'd get caught by a bird
You’d have to devise some sort of fire proof mini airlock, large enough for a laptop or whatever the largest device you expect to deal with. This would be pretty expensive and not very practical, but even if it was, then you’d have to deal with the ethical and legal issues of where it lands and whether or not it might cause a fire there too, to say nothing of injuring someone or damaging property.