The skins thing is an issue for me personally but other map makers may not care about it. The main problem is likely to be the summer base terrain, object and clutter textures sticking out like sore thumbs in the snowy winter terrain. This is a total immersion killer whether you are sitting in a GV or an aircraft, basically it looks crap. Map makers are not allowed to replace these in an MA terrain like they can in a special events map and I think that is the main reason no one has done a winter MA map.