Its amazing that the Dome, built as a publicly owned venue, had such emphasis put on it for baseball when the Jays were barely 10 years old at the time it was designed while the Argos had been around for well over 100 years.
Its bad enough they had to butcher Exhibition Stadium just to get the Jays, they had to go ahead and build a dome just for them too with $650 million 1980s dollars. Thats probably well into the billions in today's money...
You can also see hints at the desire for an NFL team in its design as well. The endzone 500 level seating has a line of sight that truncates the last 10 yards of the south endzone for Argo games. This conveniently is also just behind the location of home plate in the baseball configuration and just behind the location of the dead ball line in the NFL configuration.
Continue the slope of the 100 level around the open endzones in the current CFL configuration with foldout seating and voila, you have the perfect floor space and sight lines for an American field.