I was kind of imagining the battery packs being used more-or-less as-is, maybe broken down into individual modules, but not down to the individual cell and reas

I was kind of imagining the battery packs being used more-or-less as-is, maybe broken down into individual modules, but not down to the individual cell and reassembled. That just seems like a lot of work, and you'd probably get bad results if you mixed cells with incompatible charge/discharge curves or whatever. I could imagine a facility where each pack is separate by a non-flammable barrier (concrete, firebrick, or whatever works in this case) to stop one out-of-control pack from igniting its neighbors. And then larger groups of packs being segregated from each other with thicker fire barriers, and so on. And coolant constantly pumped through the facility: the batteries, and maybe even the fireproof barriers between packs. The whole facility can be located away from cities or towns, so fires don't cause (as much) of a health hazard. Maybe a ventilation and filtration system that can capture the smoke and filter the worst pollutants in the event of a fire. This whole thing sound kind of messy to build, but then again it's just a centralized version of the related idea of using people's cars connected to smart bi-directional chargers as a backup power source for the grid. If it can (theoretically) be done with a bunch of geographically distributed individual cars, then it ought to be possible to do something similar in a centralized way with whatever safety precautions are needed.