You absolutely can design a firewall system able to fully contain a runaway pack. They have small systems that look like briefcases to nab runaway laptops on p

You absolutely can design a firewall system able to fully contain a runaway pack. They have small systems that look like briefcases to nab runaway laptops on planes, for example. But when a cells goes, it goes. No fan is going to remove anywhere near enough heat. And you wouldn't want it to spread the vapors, as HF is a genuinely dangerous byproduct. The only real solution is full containment. And being 100% confident in your containment solution would require a lot of destructive testing- it isn't a trivial problem.