Question: Suppose I want to reduce risk of a circuit breaker malfunctioning and failing to disconnect a shorted circuit.

What if I install two identical breakers sequentially (one after another) so that if one of them fails the other one steps in and disconnects the circuit? Is there any problem with such installation?

Answer: 
Most generator manual transfer switch-over panels require you to do just this. The wire coming out of the breaker and going to a load (normally) is disconnected and channeled over to a second panel with another breaker and then then the biter-end coming out of the second panel is tied back to the load. In short, two breakers in series.
Putting two breakers of same size and rating in series can be dangerous. manufacturers give the short circuit breaking current for ONE device.
Modern CB operated with the magnetic force generated during the short circuit. This magnetic repulsion of the contacts is linked to the energy generated during the short circuit. The breakers are designed to open according to this energy generated during the short circuit. the opening time and speed is defined according to this energy. If two breakers are in series it impossible to predicte the energy at the level of the two devices. The energy is distributed over the two devices. And the operation time and openning speed can be slower than with only one breaker. Putting two breaker of same size and same rating can be dangerous.