I sense there are two issues here
the one that everybody seems to be talking about here is the failure of a single non-critical system in a spectacular way (see photos in previous posts)
Identifying and fixing the root cause only minimizes the risk to an unknown level since any battery is prone to failure for a variety of causes at any time.
The larger issue is the availability of redundancy and shielding should the battery fail in a critical flight regime.
I'm still not clear what the critical safety issue is that caused the grounding of this fleet. If we want to nit pick at Boeings comments then we need to understand this part of the equation.
For starters I am looking for expert comments on how necessary such a battery is to safe flight operation?
Secondly was this fire contained in a manner presumed in the original certification documents ?
It's one thing to have a precautionary landing and quite another to have a forced landing as this can be addressed by updating SOPs (still leaving the pilot to decide)