There is an alternative way of preventing fires, namely an over-all fire preventing GFI. (Sometimes used in Europe) The actual specification varies between countries, but the 300 mA time-delay type should be sufficient. There are two safety benefits to such a GFI:
1.) Reduced risk of fire in case of current to ground, when the fault path has too high resistance to trip the breaker. (Fault condition is not a "good" short or the ground conductor in poor condition, e.g. old corroded conduit.)
2.) Less risk of electric shock when a grounded object has become energized by a fault, but the current is too low to trip the breaker instantly. (In this case you can have 100 or so volts on the grounded object for several seconds.)
There is a major drawback to using a GFI in this way: In case of a real live-ground short both the breaker and the GFI will trip, leaving the house in darkness. Additionally, in this case the GFI was of no use.
In the case where the GFI trips, but the breaker does not, it may have saved someones life but the user will have to trip all the breakers before resetting the GFI, and then reset the breakers one by one to find the faulty circuit.
(I don't think nuisance trips is a problem with a 300 mA GFI. The time delay will also ensure that it won't trip if the fault occurs on a circuit protected by a "normal" GFCI, GFI-receptacle or AFCI.)
Just a thought.