How about a route like this?
Disclaimer - This is rough drawing and I haven't planned for exact routes and turn radii, ridership potential, etc. This is just an idea.
View attachment 451022
It's a 12+ km route with 10 stations (maybe West Mall station can be skipped). I have deliberately chosen a diagonal route so that this route doesn't just cross all major north-south roads but also major east-west roads such as Bloor, Dundas and Queensway. That way it will intercept multiple north-south and east-west bus routes. The areas around the stations alone won't be enough to generate demand.
It may seem like the line is going under the houses all the way but it's only going under houses between Bloor-Cawthra and Dundas-Tomken. At other diagonal routes, it's either going under parks or industrial/commercial areas.
Can subway go under houses? I believe so because they are already doing that with Yonge Line in York Region. Once we see how Metrolinx is able to tunnel under those houses, we'll know if Metrolinx can replicate that here. The route can be planned in a way that ventilation shafts or emergency exits are somewhere on the internal streets instead of someone's backyards. They may still need to buy some people's front yards.
I have added a station at Confederation which some people may feel unnecessary. Burhamthorpe and Confederation is the centre of the density at MCC (not Square One itself). Mavis and Hurontario stations are 2 km apart so having a station in between a dense area is not superfluous. Right now there isn't that much density at Mavis but MCC is expanding west and that station will be become necessary in 20 years when this line could be built.
I am sure there would be many loopholes with this route and I would like to hear everyone's thoughts.