Integrated lights on a helmet could work well, sure. I wouldnt buy one if the helmet weighed an extra 100g though. And the light would need to pop out easily for charging because its dumb to have to plug in an entire helmet.
Having 2 rear lights on different parts of the bike, one in solid mode and one flashing, would help make someone more visible. This option is probably cheaper and lighter than a helmet light.
Earlier this year I bought a MET Rivale MIPS helmet. Prior Rivale helmets were designed to accept a flashing light made by MET that easily connects and disconnects for charging. If it fit my helmet, I would have bought it because the design is 6 small LED lights that curve for more visibility at angles, its $40, and there is a smart setting that auto turns the light on in dark conditions(tunnel, heavy shade, etc).