Far from impossible:
That's a pretty wide curve if utilizing Corporate Dr as right-of-way to Bellamy.
The best we can hope for is diverting the Sheppard East LRT and SmartTrack monies into extending the subway to Morningside Hts. With the subway stretching all the way to Finch East and Morningside, it gives a sort of mission accomplished for all of Scarborough.
Keeping with the direction of the discussion, we don't need a hub-and-spoke model for Scarborough per se. I'd gladly be happy seeing 8 new stations averaging 10-20,000 daily users each than one hub totaling 100,000. Spread the wealth.