Singleplayer armors can`t really be called skins, as they are all separate armor pieces, each with its own stats, modifiers and localized armor value. In MP the armor value is NOT localized, but universal for the whole body, and the damage to body parts are defined with different modifiers, always taking into account the universal armor value and type. For example if you have a 45 armor soldier that has a full helmet , and another 45 armor soldier that doesen`t have helmet at all, if both of them got hit on their head for the same amount of damage, the damage recieved would be the same for both.
Which not only does not make sence, but is a mechanic i personally strongly disagree with. Not that TW would ever make a class with such a discrepancy in its armor value and loadout appearance, but that is how it would work.
So skins would only make you look different, and emulate Singleplayer armor loadout artificially, but not nearly as close.