The challenge of course is that there is a very small window of time where you might suspect the pack will catch on fire and it’s feasible to be close enough to a battery pack to be able to plug something into it, without being horribly burned because it’s on fire.

That length of time may be zero if the reason it is on fire is due to traumatic damage to the battery pack from a crash or similar.

It’s easier and less error prone to spray it from a distance. If it isn’t on fire yet, maybe it keeps it cool enough it never starts. If it is on fire, just keep spraying until the bad flames stop.

Teslas (and maybe others, I don't know) already have liquid cooling passages and piping leading to the batter pack. I do not know how feasible it would be to add a tap to that system.