Whoa, congrats on (almost) getting into the game :)! Anyways, this was always a really good idea and I think it could be in for mobs in the future! Support
You misunderstand. My diagram here was a suggestion on how to redo the original skin layout in such a way that it would grant us space for texturing both arms and legs while still fitting within the 64x32 image size. Also note that this suggestion is several years old.
Snapshop 14w03a introduced a different take on what I proposed. They use a completely different mapping which also includes extra space for additional "hat layers" for the rest of the body. It is entirely different from the layout I thought up of.
But had you not made the topic, there would have until very recently been none to express the need of a re-take on how to create skins. Your input in this implementation remains that of a suggester, since what you really suggested was to be able to include asymmetrical limbs. Mojang looked at this, as they usually do, and implement the part they like, combined with features they themselves see fitting. I really must thank you for making this thread!
I use a skin maker called Skincraft on Newgrounds. I have a skin that has 64x64 and all it does it use the actuall skin and excludes the extra (jackets, hats, arms and legs).
Refactoring the Player Skin for added detail (ALMOST IMPLEMENTED)