The task appears difficult because fires seem like a moving target. Who has not heard the old saw that "No two fires are the same?" It is true that the risk posed by a structure changes by day and time of day. For example, a fully occupied building poses a greater risk than an empty one, but the same building can have both attributes depending upon the time of day. The time delay between ignition and reporting changes the risk. A fire that is quickly reported poses less risk than the same fire if reporting is delayed.
There are a lot of other reasons why risk varies. However, fires are comparable because they all go through the same stages of growth. The way around the barrier of risk variation is to describe fires at the same stage of growth. Enter flashover again. The policy makers should already be convinced of the impact of flashover on victims. Now it can be used to explain the impact on fire department resources.