Sounds like it could also work as a hot-swap battery pack, where you could drive up to a carwash style apparatus which takes your low charge battery and puts in a fully charged one.

Could help, but could also add a lot of weight and complexity to handle an issue that is exceedingly rare.

Do ICE vehicles ever eject their gas tanks?

In the majority of cases, its still going to be stuck under a mangled car that you cant move because it is on fire. A better solution might be to route multiple ‘flood tubes’ to the battery compartment and place them in easy accessible places. That way you would just need to pop pff an access panel and hook up a hose.