I would absolutely LOVE this. But sadly, I don't think the creators of minecraft WOULD implement this, 1. minecraft skins are stored on servers, with the current amount of minecraft users times the amount of anim frames, would lead to a VERY laggy skin server.
2. every server would have to lose its backwards compatibility (or disable this feature, which would be sad.)
3. People could make WAY more graphic skins now, and servers wouldn't even know it because it only shows on one frame
4. this could be cheating on certain servers.
Like I said, I would LOVE to see this implemented but I don't think its an option :/