The best and most affordable option was the one that was never proposed.
The city can`t afford a tunnel by itself, a grand blvd is nice but I don`t think it could realistically carry the capacity, and no matter how they design an elevated route it will still be a bit of an eyesore and act as a psychological barrier to the waterfront. The option?……….GIVE {or at least sell the city lands near the Gardiner at a greatly reduced rate} to the developers along the route which mostly owned by the city, have them build a trenched tunnel under condos they can build above it. It`s been done thousands of times in Toronto...…….it`s called a parking garage.
The only difference is that the height will have to be higher than a standard parking garage and instead of cars sitting there all day, they simply are travelling thru. The city would pay for any larger gaps between condos/office towers, building the end connection to the DVP, and be responsible for maintenance which they could pay for by selling the current Gardiner lands which will become available once the current elevated structure is torn down. The Gardiner will also be protected from the elements so will require less maintenance especially by a lower speed limit and the city gets it`s connection while the highway being `out of sight and out of mind`.