So the real danger from cells that have been deep discharged is dendritic growth as we both know.
Yes dendrites could develop later on. But the process of dendritic growth is quite slow and gradual.
Because of that, before the cells start getting too hot and threaten thermal runaway, what will happen is that the pack will run out of balance faster than the 40mA my BMS can balance. And shortly after my BMS will trip protection and I will be safe. This is actually why BMSs have a lower balance voltage - 1mA is of course not enough but they tend not to exceed 50mA so they will catch damaged cells very early removing all the risk.
As for deep discharge, you might enjoy this paper : https://www.nature.com/articles/srep30248 which also includes a short literature review.
The TL;DR is that damage is relatively limited during deep discharge even to 0v. There is plausibly possible capacity degradation but it not very different from accelerated wear and tear, though the authors did not detect any.
What is really dangerous though is discharging a battery pack to 0v - when that happens it's easy for some cells to gain a negative state of charge, which is when the nasty stuff that actually causes fires and damage happen.
Copper dissolution according to this paper in more modern batteries does not even really happen until -12% state of charge. Indeed in modern higher capacity batteries they found no detectable damage at all until -12% soc.
Because of that, I am very confident from my setup - the risk of internal short circuit is incredibly low given that I know that the cells were always in balance, and any slow-forming internal short circuit will trip the protection much before there is any fire risk.
It's very interestinf though from reading the paper that the deep discharge risks essentially disappeared at 0v from pure coincidence as capacities increased though, I'd have expected somewhat the reverse :)
