^ A continuous ECLRT + SRT will require full grade-separated Eglinton East which is a nontrivial additional cost; about $2 billion for going underground, although it can be less than that if some sections are elevated. Plus, such configuration is going to shift a lot of riders from Danforth subway to Eglinton, and risk overwhelming Yonge between Eglinton and Bloor.
"Plus the lack of running up to Sheppard would've avoided the cannibalizing of Sheppard East's ridership." I can't agree with this statement. If the riders, given a choice, prefer to go south or south-west instead of staying on Sheppard and going west - then they must not be forced to go west by the lack of southern connection. Sheppard route should be left for those who actually needs to travel west.