I am currently experimenting with pants. I have tested MEC's River pants. They are made of Supplex nylon, they are really quick drying. Apparently bugs can't bite through them. They do break the wind, they are really tightly woven. But they are not warm at all and below freezing, I wore them with a pair of wicking long johns. When they lay flat on my skin, I feel the cold conducting and chilling my legs. So you need to layer a decent pair of insulating pants underneath it. There are also nylon athletic wind pants that have a polyester lining like the Nike brand that I would like to try out.
Now I'm looking for wool pants. I checked out dress pants on the market but they don't make medium weight serge wool pants anymore. It's all super 100, super 130 extra thin italian tropical pants. For colder wheather they recommend flannel pants but they don't shed the snow well and are not that thick.
So I'm looking at Filson and Cabela's whipcord pants, they are midweight and have a twill weave (diagonal ribs) which help shed snow. Ideally I would wear them with suspenders so that the warm air produced by the upper legs can flow freely to the upper body. One advantage of wool is that they are fire retardant, which is a benefit when you work with fire. On the other hand, you can't launder them the same way you do with other fabrics. Cabela's whipcord have a SW100 finish so that you can machine wash them. I'm not sure what it stands for, maybe steel wool 100g? I may ask them for more information about their miracle finish.
I'm also looking at moleskin pants, which are made of heavy cotton fabric, woven and then sheared to create a short soft pile on one side. Apparently they are very warm but I would wear them in dry cold conditions since they are cotton. The military pants like the BDU always have cotton fibers in them because they need to be quiet.
The lower body requires less insulation than the upper body generally. Just look at the scottish people wearing kilts and skirts. In fact Mountain Hardwear makes a technical kilt. It seems like a good idea, given how easy it is to put on and remove:
Choosing the right clothing is such a complex topic and I find myself asking questions about this most of the time on this forum. ¾ of your survival relies on the clothing you wear.