First - preventionSo what is your plan in advent of a thermal runaway event?
As reperated many times - we try do not overload the cells. Low discharge "C" means that you can keep the cells not even warm. I am carefully watching temp. on cells to see if there is not temp. increase. 30-40°C is max.
Second - monitoring
You have to know temp. on each battery pack. It means if you have for example 27S 5P you need 27 temp. measuring points. All time monitoring is necessary. When temp. raise above 40°C, you need to know it. Some of my friends are flying with battery temp. arround 50°C and from my point of view that is already a lot. This is valid for discharging as well as for re-charge.
Third - emergency cooling
Of course you can still have problem with damaged battery cell. As prevention try to do not manipulate with batteries unless is necessary. As you can see - I am not a fan of removable battery packs. There is always risc of mechanical damage etc. They are existing high pressurized plastic tubes able to cool down the battery packs. We don´t have this system actually installed, but is under testing. It is emergency system able to give you time reserve to make emergency landing.
Most lithium-ion (Li-ion) cells must not be charged above 45°C or discharged above 60°C. These limits can be pushed a bit higher, but at the expense of cycle life. In the worst case, if cell temperatures get too high, venting may occur, resulting in battery failure or even a cell fire.