[1overcosc]

The 417 should be extended eastward as a full 400-series freeway (ie. full grade separation) to Petawawa or maybe Deep River. From there to North Bay, leave it as is, maybe add a few passing lanes, because traffic there is very, very low.

Between North Bay and Sault Ste. Marie, twin it, but not as an expensive 400-series freeway, but rather as a Prairie-style "dual carriageway", that only puts interchanges at key junctions and leaves most minor roads with at-grade intersections. Do this for the segments between Nipigon and Shabaqua, and from Kenora to the Manitoba border, as well. Leave the rest alone, again with some more passing lanes.