@Chris Scott
Quote from USMCProbe (my bold):
"Have a bunch of closely stacked cells being fast charged and discharged in series seems like it would be a really bad design."
All that works for the better part of 100 years, in every vehicle with an electrical system, including aircraft and submarines, as well as with big stationary 48V telco batteries and data center UPS installations. LiPo powered vehicles deserve special mention.
All those are serially charged and discharged. Balancing by bypass is used in all large installations, except NiCd perhaps, not sure there.
I think OP was referring really to the closely stacked cells, which probably is one of the weaker links in this system. Fortunately the box held up, although barely, but it did. Practical battery management is weaker still.
IMHO the weakest link so far is the response to those 10 batteries ANA had to replace. Alarm bells should have gone off no less than after having swapped 10 Engines.
I guess electrical systems must be harder to understand than turbines.
Shades of gray without black and white answers.