It's not going to happen on the cheap. Achieving a failsafe design with no single point faults puts the application into the realm of personnel safety circuits with monitoring, diversity, and pre-emptive fault detection. To get something at least plausibly unlikely to fail simultaneously that wouldn't cost too much, you need dual diverse systems, that is, not identical and operating differently with different components, that have no common-mode failures such as a dead battery, bad ground, or a single blown fuse.
My primary concern with the incandescent hot light is that the light is simultaneously the only warning and also the most likely component to fail. Maybe there's a chance OMC at least tried to extend its life by making it, say, an 18V filament that only sees the typical 12.6 V(no charging) or up to 14.7V (during charging). At the suggestion of some here, I addressed the potential failure of the lamp by adding a sound-generating device as a backup, which apparently is still unsatisfactory to some compared to "what ya shoulda done".
I've got to say, fellas, your collective habit of crapping on people's efforts in a non-constructive manner, making off-topic / irrelevant / distracting editorial critiques, and saying something discouraging instead of something helpful...makes this not a fun place to spend time or share things. I'll likely not be checking back in here too often, if ever. Life's too short to deal with the aggravation.
