As a driver, one of the main issue I have with bike lights, is that it's difficult to estimate how far away they are, unlike cars with separate right/left lights, in this case it's the distance between the right and left that immediately gives you a fair approximation of the distance. It's often almost impossible with a bike, until you can see the rider (also bike lights might vary more in intensity, so you can't rely on that either).

Adding reflective bands or tape to the pedals or ankles clearly helps to identify what you are looking at, also gives an idea of the distance, same for a reflective vest.

So maybe a light on the helmet that illuminates the vest would be a good complement to the fixed red rear light... it doesn't need to be very bright since the vest is very close...

In Europe fixed white front light and red rear lights are often required by law, sometimes also reflectors of the same colors, front and rear, as well as on the pedals! many cyclists don't follow these rules, and they are not enforced from what I'm seeing.

I believe German rules are the most advanced for bike lights, but I don't know what exactly is required, except that the lights must be approved (?) maybe someone on this forum lives there?