Looking over the maps it seems that, if the railway corridor is mainly ruled out, then a good route would be:
- From the Iron Horse at Gage, take Raddatz Park along the north side of the creek to the end of Waverly.
- Take Waverly to Strange. Yes, this will have to be on-street; I'm not familiar with the traffic here or how problematic this might be.
- Cross Strange into Cherry Park. Maybe reconfigure the parking lot so the trail is unimpeded. Upgrade the existing park trail, and follow it to Park and Stewart.
- Cross Park and run the trail along the south side of Stewart; there's only one driveway here, for the Home Hardware parking, and the trail can be kept mostly separate from traffic.
- Here's where things get tricky. Expropriate a slice of the Home Hardware lumber yard (hopefully no need to touch the structure) and bring the trail over the Huron Spur (uh oh, railway approvals needed). Then, use a thin slice of the former Kitchener works yard to get the trail to the UW lands and King Street.