>Have a metal container nearby to drop them into for transport outdoors.
Before doing that, try watching some experiments with fireproof containers specifically designed for these fires, to have an idea how quick and violent this can be, and how bad most of these containers are at preventing it from going from 0 to inferno or to a toxic cloud suffocating you in seconds. This might or might not help you plan for the worst case, or better yet forget about doing DIY battery pack repairs at all.
Before doing that, try watching some experiments with fireproof containers specifically designed for these fires, to have an idea how quick and violent this can be, and how bad most of these containers are at preventing it from going from 0 to inferno or to a toxic cloud suffocating you in seconds. This might or might not help you plan for the worst case, or better yet forget about doing DIY battery pack repairs at all.