The number of cyclists prevalent is highly dependent at the time of day and location. But suffice to say, at dusky rush hours, I occasionally see far more than 20 bicycles in the evening at large, busy intersections. I don't even want to think about my trips to China, where I've seen more than a hundred. With all of them using blinking lights I'd have a hard time tracking them all as my attention keeps being pulled from one to the other.

Another problem for blinking lights is that it is also the signal for a stop sign, or a turn signal. More flashing lights to watch for does not seem like a good answer.

I'd actually say the small area of light is as much a problem as the brightness and the flashing. A larger surface lit up at a constant moderate brightness is easier to track by eye. A small blinking dot doesn't immediately indicate a bike to me, since all can focus on is a small blinking dot. It could be a jogger or pedestrian too, for all I can tell. Two circles from glowing rims I can instantly understand as a bike, but only if it's a whole circle that stays steady. It's like a heiroglyph for bicycle.