If this is subbing for a prospective Mississauga subway, I think we should be willing to spend to relocate stations/access to future-proof as much as possible and streamline integration with transit on major streets. Cooksville and Erindale are already well-located. Dixie GO could stand to have the platforms moved closer to Dixie. Add a stop at Cawthra, protect for one at Mavis (though the area is quite industrial), a stop near Eglinton, protect for a station at Britannia, move Meadowvale closer to Derry (there is a self-storage business that could be redeveloped as part of a TOC), relocate Lisgar to Winston Churchill, add a stop at Ninth Line. We should try to align the GO stations with arterials that can be used to funnel bus passengers onto the line to make transfers quicker and have buses spend less time diverting. I expect Mississauga will be developing a BRT/BRT lite network on many of these arterials.
While we're spending $6B, and before a lot of redevelopment happens, is probably the right time to align the stations to support future growth.