If we assume average flight loads between 150-200 pax per aircraft and 1 MM pax, that works out to 14-18 flights a day. A 2 gate terminal would be fine. And it could fit in to a normal GA ops. So not really a burdensome deal. The issue, however, again, is whether splitting the catchment works for the airlines. Those passengers all fill seats at Pearson. So this leads to two scenarios:
1) Sufficient movement that the airline can cut flights at Pearson and add them in Pickering with no loss of traffic or even a net gain.
2) Insufficient movement to allow reduction in Pearson slots. So now the airline is facing emptier airplanes at Pearson and the need to service flights at another airport. That's a terrible business case.
For charters, frequency matters less but load factors matter a ton. Not one slot will move unless the airport can fill up the plane to at least or more than Pearson. I suspect this might be worse than Hamilton. At least Hamilton has a lot more potential from the Western GTA and Southwestern Ontario and the Niagara region. It still struggles with more than a few flights a day.