Honestly, I think Toronto should just be bold and install high-quality separated bike lanes across the entirety of the streetcar network, even if it's at the cost of removing parking and driving lanes.
The streetcar corridors are ideal for cycling. All the streetcar corridors are flat, crosstown routes with a multitude of small and major destinations. This are ideal conditions for cycling.
We have a massive GreenP network Downtown. Dedicating this much street space to parking makes no sense.
In many places, this means traffic will be reduced to a single lane. Some people will be fatalistic about the traffic impacts, but I don't think it will be bad. Realistically, most of the streetcar network is already de-facto one-lane operation anyways, due the the multitude of obstacles in shoulder lanes (constrction, Ubers, illegal parking, etc...). And as we've seen over and over again, traffic demand tends to "evaporate" once you remove traffic lanes.
This might lead to more reliable streetcar operations as well, since a single lane of traffic leaves cars with no opportunity to "squeeze" in front of streetcars. It also means that traffic will no longer be held up by cars trying to park.
Like the King Street Priority Corridor, this could also be rolled out on a trial basis. Just lay down some flexiposts, and see what happens over a year or two. We can always revert to the status-quo in the unlikely scenario that the impacts are awful.
This makes our streets significantly safer as well, since a single lane inherently calms traffic.
Realistically, after some whining, I think drivers would quickly get used to the new norm of parking at GreenP lots. Fewer drivers might come Downtown, but that's fine.
The network effects would be huge. This is the kind of thing that could double Toronto's cycling network utilization overnight. Toronto's cycling network would rank amongst the best in the world.
With the size of Downtown Toronto literally doubling, we'll inevitably have to prioritize streetcars and cycling movements over all else. Streetcars and cycling are the only way we'll be able to move people across Downtown effectively. They are essentially the circulatory system of Downtown.
This all is really easy to do. The only thing stopping us is fear of the car lobby.