That will be amazing! Imagine: An Oshawa to Malton trip, via Osgoode! Instead of going down one set of stairs and up another between platforms at Union, it will involve down one stairs, walk for a bit, through a turnstile, down another set of stairs, on a subway, down more stairs, on another subway, out of that subway, up one stairs, through another turnstile, up a second flight of stairs, into a new station, then another set of stairs.
Now that's regional transit!
Okay, there are other cities where you have to do that. London for example, or New York (between Penn Station and Grand Central), or Chicago, but those are the results of multiple private companies building networks 100-150 years ago. The point is that this is Union Station.
Damn it. This is the worst possible way to get our much needed DRL.