To have successful fire breaks would make the packs way bigger & heavier than they are already.I reckon the battery tech will evolve....fire breaks and compartments etc for the battery or some sort of fire protection around the battery.
I'm thinking it's probably best to do a PCP deal or lease them....once the fire stuff evolves I would imagine the first generation cars would take a big hit in value.
Also the chemical fire is internal needing no other ignition or fuel source - with incredible heat - so you'd need an extremely effective firewall to prevent the heat setting off adjacent cells.
Not sure it's very simple to solve tbh.