What might be a PC/HC way of covering a capote to fully block the wind? .
A buffalo robe or something similar.
To break the wind effectively Your outer garment should be a pull over design. Inuits made Anoraks out of seal skin and covered them with fish oil to water proof them.
I have comfortably worn a Capote in subzero weather but I had additional layers of wool underneath and I stayed out of the wind.
Liners are more for comfort where as sewing leather to the outside of the capote, breaks the wind and adds durability.
When layering clothing for cold weather you want the thinnest and finest materials closest to the skin, progressing to thicker and coarser layers as you move away, ending in a wind and water proof shell layer. loose fitting is better than tight fitting and cotton is the "death" cloth.
Freezing to death is very historically accurate.
A warm stone wrapped in cloth and placed in a pocket will keep you warm and serve as a hand warmer. Same goes for hot water bottles, hot water has the advantage of being drinkable when it cools. Dehydration is a bigger concern in the winter than in summer. Dehydration accelerates body cooling. placing hot water bottle or warm stone near kidneys or major arteries will greatly increase your warmth.