I agree with your idea of how to tax things hatman. But I disagree with
"I don't think the suburban sprawl patterns will be sustainable for much longer so it will eventually stop" statement, because it's already unsustainable and it's not stopping. Something not being sustainable, unfortunately, is not really a reason for that thing to stop in the way our society is structured. I also think that the autonomous vehicle future is a lot further away than people think, and your ideas of buses that come every 5 minutes and trains so frequent you barely ever have to wait sounds nice, but in reality, I have a hard time imagining that will actually happen.
Also, I call your picture and raise my own that I took today. Looks like the pedestrian tunnel under State Street is actually getting pretty close:
Can't really see it too well in the picture, but the escalators down into the tunnel look to be essentially complete.