Here's a possible routing I came up with:
Some highlights:
* Highway 17 is detoured around the northeast corner of Sault Ste. Marie. For through traffic, it would take about 5 minutes to go from the Rankin turn to Sixth Line (on the northern fringe), instead of about 20 minutes today.
* The northern/western terminus would be at Great Northern Road north of the ACR underpass (likely an at-grade intersection initially), although it would be easy to extend farther north (west) and build an interchange there with the configuration.
* Local traffic is connected to Sault Ste. Marie by an extension of Carmen's Way, which could initially be built as an expressway-standard road before upgrading to a freeway later. It would connect to 17 at an interchange south of Fourth Line, and would be routed to minimize disruption and avoid a conservation area.
* The Rankin turn on 17 (where it turns south to reach Trunk Road) would become an interchange serving the eastern part of SSM.
* Old Garden River Road and the ACR would pass under 17, while Fourth Line (realigned slightly) and Fifth Line would pass over 17. An interchange may be possible at Fourth Line to serve areas to the east of 17, but that could be problematic due to weaving and also due to traffic issues on a rural minor arterial (not to mention the development that would likely come to that area).