I'm usually wearing zip offs which are fairly wind resistant and I can sit without too much worry about shredding them.
Indeed, rain pants will shed wind nicely and in my part of the world, if it is cold and windy, chances are it is raining too.
IMHO, wind pants work into an UL clothing system best if you like to wear running style shorts.
My caveats are the fragile nature of wind pants. I like windshirts a great deal, but I don't sit, slide or crawl on my windshirt. I do need to watch for sharp branches and thorns, but trails are usually narrower at the bottom than three feet up, so pant legs are exposed to more brush and thorns as well as rocks, roots and mud.
They should offer some light colors for sun and bug protection in good weather.