Sorry you silly primitive, but your dream simply isn't going to happen. When me and a few friends when to Rushmore in 2010, I asked one of the Park Rangers what he thought about adding another face.
He said it wasn't possible, as the rock face couldn't support another structure. There was more to it than just that, but I made damn sure to take the time to ask when I was there, just so I can set you dumbasses straight when you pull stuff like this out of your ass.