Poncho's are one of the best warm winter garmets ever invented.
The best ones are made from woollen blankets.
Of course the enviroment they are made for, the amount of travelling and weather etc... can all be decisions in the design and material used. They can also be made with hoods and or with a variety of materials - such as a plastic overlay in wet and cold climates and to have a woolen inner poncho.
They are brilliant for an around the house garment in winter, as the wearing of a ponch AND warm clothes, makes like a heat tent, that keeps your arms and most of your body in an envelope of your own warmpth.
You FULL arms are also free of any "containment" or "restructions" at a moments notice, when you want to start cooking or working on things.
I use poncho's every winter and in wearing this, and perhaps some other clothes on the coldest of days means that I am toasty warm and I have NO heating bill.
They are also great wear while sitting up in bed or when at the computer..
So this design IS the best design, and the other issues, are secondary.
Most of the genius work in this is in making a right fitting hole with the proper orientation.
I find that a slit, across the shoulders, is about the best fit.
In my expereince, making the slit wide enough so that the material rests ON the shoulders and NOT on the shoulder / neck muscles.
Also if the slit is too wide, then it tends to allow the poncho to go down over a shoulder or shoulders.
It's smart to sew up the edges of the slit AND to add in some reinforcement so that the slit does not rip or wear open any more. Use the humble blanket stitch.
Here is my pattern for them.