Recommendation for an outer shell

[Kolesar]

4. I have a single-layer waterprooof/breathable jacket by Pearl Izumi and it's da bomb!

It has pit zips for super ventilation. Since it is single layer, it stuffs into my jersey pocket. Yes, it was expensive, but it won't tear easily and the stitching will stay taught for a decade.

My other trick is piece of waxed paper that I put on my head if I get cold. Rather like your plastic bag

I finished a tour with a plastic bag under my shirt when the day became cloudy and clammy. I was coming down with a cold.