I'm actively considering wearing a long sleeved t-shirt instead of a vest on my rides. I've definitely got softer since moving down from the North East. I'd normally ride bare chested in this weather.
But in all seriousness. I'm four stones lighter than last year and I've been riding 100km audaxes in subzero temperatures wearing
Roubaix tights, a Canterbury base layer, a cycle shirt, a cycle jacket and a diaphanous windstopper layer along with a pair of Gore winstopper gloves. I've never worn overshoes. I've always been blessed with good circulation to my extremeties.
I carry a spare layer or two with me but have never needed to wear them.