Yonge and Bloor would be a good place for something at a gentle one thousand to fifteen hundred-ish feet. It could have an effect much like the placing the Empire State Building in the predominately low-rise Manhattan midtown of the 1930's did.
Ideally, I'd like to see it replace the Hudson's Bay Centre - but just across the corner would work well, too.
What I'd really like to see is a cluster of talls and very-supertalls on the North Portlands, abutting the Keating Channel. Six or eight hundred through two thousand or more feet. (sigh) That said, some of the West Don Lands wouldn't have been a bad place for a well-composed cluster, either.
Foster, SOM, Eisenmann (possibly? I wonder what he'd come up with), Zaha Hadid, Pelli, Calatrava....and just to make veins pop on foreheads and elicit screams, Robert A.M. Stern.