You can't mount a light to it, but I've seriously considered rocking a Giro Air Attack Shield for the coldest of winter days. But that would be pure excess that I can't actually afford.

I generally wear a hat underneath, even in summer (more of a fashionable sweatband for me), however if Giro is a good fit for you, I've actually been pleasantly surprised with the Savant, and it would have less ventilation than your Atmos. I bought it accidentally because I forgot my helmet for a group ride, and it ended up becoming my daily helmet. Retail is 90 bucks, and can probably be had cheaper. Honestly, it's nice enough that I'm not sure if I'll ever let myself spend the near 300 bucks on nicer helmets.

I haven't tried to mount a light to it, though. There is ventilation directly down the center line, so you would have to be wrapping around two sections to get a centered mount. That might not work well inside the helmet fit-wise.