This is starting to get really off-topic, but it still related to the Waterloo Region transit plans, so I'll entertain it a bit longer.
I really think taking rail service much past Galt is rather far-fetched. Once you get past KWC, you're getting really out of the Toronto commutershed; a stop at Highway 97/401 is in an awkward spot for serving park-and-riders from any major community to the west extreme fringe of Toronto-bound commuters. If GO train service is extended to Cambridge, the best place for the big park-and-ride would be at Puslinch Station (Highway 6 South) so it could serve Guelph, Kitchener and Cambridge with easy access of the 401. There simply isn't the room at Campbellville even for a 12-car train platform and a park-and-ride, never mind a big lot. There isn't a tonne of redevelopment possiblities at Galt ("The Delta") but it is the only transit-friendly spot for a station.