I agree about the need for express service across the GTA, but it should be GO rather than VIA.
VIA can't afford to have trains sitting idle all day waiting for rush hour. If an early run from say Niagara Falls arrives in Toronto with a load of commuters, but then doesn't have an assignment for that trainset for the rest of the day, it's not sustainable within VIA's resources or business model. Similarly, VIA should not be running empty seats from London or Niagara to collect passengers for an Aldershot to Union ride.
It's not that GO likes having trains sitting idle either, but all those empty peak-only trains are folded into one storage system and one investment decision very much based on avoiding/relieving highway congestion and emissions.
I will admit I have changed my tune on this a bit, and it should be a separate layer above the "stopping" GO service in light of trip duration, but it may be a better way to keep left and right hands organized.
- Paul