A lot of the paths I ride on have trees and bushes that tend to grow over the path, especially in summer
Also some of the proper roads have bushes that grow over the road to some extent. It is quite common for me to feel leave and small branches brush on my helmet as I ride past.
I also often feel the helmet brush on the brick/stones of canal bridges as I pass under
WHen I see lights and cameras mounted like this it reminds me of an incident a few years ago where I was riding down a local road - actually over a railway bridge and on the downhill bit - so I was going at a reasonable speed.
Suddenly my head was yanked violently backwards - luckily in a straight line otherwise I would have crashed off badly.
Turned out that a bush was growing slightly out over the road and a brach - only about 1/2 inch thick - had managed to jam itself through one of the holes in my helmet and stick in.
As I carried on it didn't and hence yanked my helmet - and hence my head - backwards.
The idea of putting extra stuff on top of my helmet to give leaves and branches something else to tangle around seems like a scary concept to me!!
Just my experience