My car has "always-live" convenience outlets (e.g., the ubiquitous cigarette lighter plugs) which incorporate a protective monitoring circuit that keeps them live, but disconnects them before the battery charge state reaches the point where it will not start the car. It seems to me that if it can be done in a car, the Boeing system could monitor battery state and "disconnect" the towing lights when the battery charge state reaches a low, but not damaging state. Full use (even to the point of damage) would be allowed for in-flight non-routine operations (gen failure, etc.). The SOP would call for battery replacement after such an event.
It's interesting, I read the list of "improvements" to the battery system proposed by Boeing, and many of them were things that I (and others) suggested early on in the thread. It seems to me that if these things are obvious to me, they would be obvious to anyone with even a modicum of engineering experience. Given that, I can only conclude that the battery system at Boeing was designed to the requirements of the bean counters rather than the engineers. And is so often the case, designing to a price, has a price, and Boeing sure seems to be paying it.