That'd be my top choice too.
And earlier I wasn't saying that someone can't put on a ton of muscle to play a part. Obviously, from the examples listed, it's highly possible.
But... what I was saying is that DiCaprio has the wrong body type to bulk up like that. He's got narrow shoulders and a thin bone structure. It's got nothing (or not much) to do with the muscles... his frame is just wrong to put on that kind of musculature. He could become lean and obviously strong, but you'd need a serious rubber suit to make him look anywhere near as brawny as other good choices for the role could get naturally. Matt Damen, Will Smith, Hugh Jackman, they've got a good frame and a good body style for adding a lot of beef. Leonardo DiCaprio, John Leguizamo, Chris Tucker... not so much.