As I understand it, the skins will be part of the terrain file download and cannot be changed by the user.  So, if we get a desert terrain, we could have desert camo planes, etc.  I imagine that it'd work in the MA (when the arena resets to a new map, the planes get new skins) but its main use seems to be for scenarios.  When we get a map for a scenario, we can get custom-skinned planes from historically-correct units along with it.