Great location for this tower, and I love the setbacks at the top. Though it looks like the skinny face will face the lake, much like One King West. I'd rather the skinny side face east/west, as this would extend the skyline east when viewed from the lake.
As for materials, one would expect to see stone mimicking the historic base on those lower sections, and mid sections, then glass and steel above that. But that remains to be seen until we see actual renders.
"Then each time Fleetwood would be not so much overcome by remorse as bedazzled at having been shown the secret backlands of wealth, and how sooner or later it depended on some act of murder, seldom limited to once."
Against the Day, Thomas Pynchon