Summerhill would be a good start. We'd have to look at creating other nodes.
That said, not everybody is heading downtown. And not everybody needs to go to Union. They do so today because of the current network configuration and fare rules. How many people would get off at Bloor, Danforth, Sheppard West (in the future) or Kennedy if we had integrated fares? Or at Agincourt if the Sheppard line reached there and we had integrated fares?
Also, more frequent service with greater service availability throughout the day might actually smooth out demand.
There's a lot of things we could do to manage this demand. We shouldn't be making excuses to not even attempt these changes.
Exactly. In fact, there are many locations within Toronto that could be some pretty major transit hubs if properly integrated. The 3 that immediately come to mind for me are Agincourt (Crosstown GO, Stouffville GO, Sheppard transit), Dundas West (Milton GO, Georgetown GO, B-D Subway, possible DRL), and Eglinton-Black Creek (Georgetown GO, Barrie GO, Eglinton LRT, possible DRL west, Jane LRT).
And of course with each of these hubs would hopefully come increased density surrounding them, be they office or residential.