Maybe you’ve already made a decision on this but in general I run one helmet that tests well on the Virginia tech tests https://www.helmet.beam.vt.edu/bicycle-helmet-ratings.html
Then I use a buff/hat under the helmet on colder days. This is usually good for me down to freezing temps, generally I don’t ride much below that since I don’t have studded tires at the moment.
What will happen first Ballard link or missing link? If either happen in the next ten years I’ll be happily surprised. But regardless it’s important that we continue to push forward these plans.