I've been thinking of a possible route for a small extension of the Bloor-Danforth line to Sherway gardens, and came up with this:
It would have 2 stations, Highway 427, and Sherway. (shown by the black boxes) The Highway 427 stop would act as the new terminus of the Mississauga transitway, as well as all the Dundas buses. I have provided a bus only offramp from the highway for this, marked in red. It would also contain a large commuter parking lot marked in grey. As for the sherway stop, it would be very similar to the current Don Mills stop on the Sheppard Line.
Costs would be fairly low, considering only 750m of this extension would be built using a tunnel bore. Of the 3.5km extension, it would require 2 widened rail bridges, 1 widened rail underpass under the 427, and a underpass for the Subway trains to duck below the current rail tracks. I'm guessing that we are looking at around $700 million for the entire extension.
I would also recommend that the extension is brought to Dundas and Hurontario, but that would make the extension 9.5km long, and costing more than the Spadina extension, which is something I don't want to do. that part of the extension can be put off to a later date, while this can be done now to provide some great benefits to the network, as well as unlocking the development potential of the sherway gardens parking lots.