I wouldn't do the tooting thing man, not on a pavement. That biker was bang out of order doing that to pedestrians. He needs to get some patience and go with the flow more...
No way for a top of the helmet kinda deal. I understand your appeal as I had the same vibe for a helmet cam.
Yet I already tried that system and it looks ragged, the viewer is shaken and disorientated by the head movements and so on. It's also the method by which I lost my old camera.
Some Vlog bikers like to use that system though as they have a microphone linked in under the helmet.
For me I like the tank mounted system better. It keeps everything stable.