Id like tc with a few tweeks like the sheppard transfer. Then electrify the richmond hill, the barrie, and the brampton line. By the way switch the richmond hill line with the cn line so there can be a easier access station at leslie and eglinton. Make all these lines 15 mins apart and add stations where ever each line connects with eglinton bloor or danforth. Then make the GO a added dollar if you have a metropass. That should make both a local and regional network.
Why would you do almost every line BUT the Lakeshore line (aka the one with by far the highest ridership)?
I do agree with switching to using the CP line for part of the Richmond Hill line, and for placing new GO stations at strategic locations within Toronto.