This is the exact type of road improvement that I am in favour of, as it makes better use of the existing road network by adding short little links.
Since I started heading down to this part of the city on a regular basis, there has been one traffic experiment that I would be interested to try. A significant component to congestion is caused by merging traffic at onramps, and weaving cars. Why not see what would happen if the westbound Gardiner was reduced to one lane wide west of Jarvis, two lanes wide west of York, with a return to three lanes wide west of Spadina. The westbound offramp at Spadina would be closed to prevent weaving of cars west of York.
If that is done, it would mean that rather than merging with an already congested highway, cars entering the westbound Gardiner at both York and Spadina would get their own lane. A question that would have to be answered though is how much congestion would result by reducing the number of lanes from three down to one or two between Jarvis and Spadina.