To rebuild the meeting space on the east side you would take out the green space. You would also have to redo the parking structure that is under the green space. You could then reconstruct what you just tore down and reinforce the foundation of the hotel as it needs to drop ~20 feet in elevation to connect to 2nd.
Then you can demolish a few hundred thousand square feet of a fully occupied Williams building (including the cafeteria, data center, gym and sky bridge to the hotel) and extend the road a further block to hook up at 1st.
The result would save a one block detour. Someone else can figure the price on that, safe bet it is in this format $X00,000,000.00 (solve for X).
Stopped future super blocks should be a no-brainer. If there are super blocks that have a path that can be a road, or are underutilized, or can be tunneled under...lets talk. But why do we keep discussing tearing down structures portions of downtown that are dense, heavily utilized, and would cost hundreds of millions of dollars? The cost benefit is dubious, and the chance of ever getting funding or public support is zero.
A well-placed meteor strike would save millions or a billion or so.