I think the Highway 7 upgrade should be along a new ROW, rather than following the existing one. There are some stretches of the road that are through wide open areas, but substantial portions of the highway have homes/cottages on both sides of the road. And some areas are pretty winding.
For example, from Carleton Place to Perth I think it should go south of Mississippi Lake (the current alignment goes north of the lake and then dips south). When you look at the terminus point of the 4-lane Highway 7 expressway leading into Carleton Place, I think it was designed for 7 to veer south, with an exit going straight into Carleton Place, much like the 400-11 interchange north of Barrie, where the 400 exits off and then veers left. Because it's quite clear that they don't plan on making it a full expressway through Carleton Place, given how much development is right along the current highway.
On a separate note, a Highway 415 from Carleton Place to the 401-137 interchange (the approach highway to the Thousand Islands Bridge/I-80) would make sense as well. Passing near Smiths Falls of course.
I personally think that the 416 was a mistake. Building the 415 connecting to a 4-laned Highway 7 which would then connect to the 417 would have much better served westbound traffic. Eastbound traffic could be served by a twinning of Highway 138 (would become 438). 416 is in a really awkward spot, because both the Thousand Islands Bridge and the Cornwall Bridge are much busier than the Prescott-Ogdensburg Bridge. To access either of those two bridges, drivers need to use the 401, which is already pretty busy. Aside from Kemptville, from Barrhaven all the way to the 401, there's pretty much nothing.