I have shot skiing events and outdoor wildlife in snow. The one thing I do is to use at least -2/3 EC to combat all the reflected light off the snow. I haven't had issues with equipment in the cold. Typically I'm shooting in the teens or higher, or I'm not shooting
I do know you want to have extra batteries, kept inside your coat where they are warm, so that they hold their charges better. Another tip, have some large ziplock bags for any gear that goes out and has to come into a warm humid environment. Place everything in the bags, seal em up and let come to room temp before you take them out. This will cut down on the amount of condensation that forms on the cold surfaces when you go inside. Other ideas that come to mind, a set of square ND grads to darken overly bright parts of the frame, a polarizer to mitigate glare, and spares of anything you can think of that could be dropped, broken, lost, or frozen. I find that I have to practice simple tasks with my shooting gloves on, since things get really awkward in the cold with layers of clothing and the like.
Hope this is useful,
Chris