It would be nice if the Ontario Line stopped or had an entrance at Ontario Place itself, like Montreal with Jean-Drapeau station at Parc Jean-Drapeau. It would reduce the need for the costly proposed parking garage and relieve congestion in the area (instead of inducing it by building a giant parking garage that will encourage people to drive).
Despite all of the investment in transit, the city's current congestion is extreme and reaching a crisis point. Everything that encourages people to drive downtown, from the presence of expressways and parking, needs to be reconsidered. The assumption that no parking means that your business or institution will fail needs to be questioned and reconsidered, as it isn't true. It's encouraging congestion, pollution, noise, and aggressive driving throughout the region.
Sure, Exhibition Station will be quite close, but having the stop in the park or at its entrance would encourage people who don't normally take transit to take it. As silly as it sounds, driving tends to decondition a lot of people to believe that even a short walk is an unacceptable hardship they should refuse to endure.