Different Opacity support on skins outer layer

Outer layers of skins should support different opacity levels. I know we have this in java settings menu already but you have to turn the whole layer transparent and the same level across the whole layer but this would be baked directly into the skin with no need to go into the settings. This would let us add glasses or glow to our skins in an easy way. Also any skins with an inner layer with an opacity less than 100 should automatically turned to the correct color with max opacity in game.