Not necissarily a comment on your post but moreso a continuation of my thought process on this topic and I don't want it to be read and not have context.
Does anybody know if there is enough room to drop the Yonge portion of the line down below the proposed DRL east extension so that it can serve the waterfront?
Having Yonge do that much of a zig-zag would be somewhat difficult. However, if you extend the Yonge line further west (to CityPlace for example), then it may work. But as the configuration is right now, it would be an engineering nightmare.