User blog comment:Llama919/Possible Beast Titan Identity?/@comment-5774380-20150620134402

That picture of the Beast Titan is not an early design, at least not of Mr. Smith. That design was revealed by Isayama the last year stating that it was a new character and saying that he "holds the key to the series". That's why he was named in fansites as "Mr. Key", and his identity was completely unknown until it was revealed in the recent chapter that he is the Beast Titan. Mr. Smith had already appeared by then.

Also, in the image of the recent chapter are still visible the differences that I mentioned: the shape of his head, his nose and his eyes, and the absence of wrinkles reveal that he is a different character. The overall features of the Beast Titan clearly show that he is a young man, much younger than Mr. Smith was even at the time of his arrest.

But I see that you like your theory too much and you will make up some explanations for whatever I say you in order to keep it; and ultimately, you can. Though as more twists are added, more fanciful and improbable it becomes. The Beast Titan is evidently not Mr. Smith, but if you like to believe that he is, I will not cut off your fun. I just hope that in the next chapter the Beast Titan has more interactions in his human form and we learn more about his possible identity.