Some of the worst examples are Highway 9 - which still exists in two separate sections as the section between Harriston and Orangeville was downloaded, and Highway 3, which is now three separate sections (Fort Erie to St. Thomas, but not including the section through Port Colborne, and between Leamington and Windsor).
I'd like, most of all, for Highways 2 (as the alternate to the 401), 3, 4 (at least to Highway 10), 7, 9, 11B (in Timiskaming), 17 (east of Ottawa), 19, 21 (south of Highway 402), 24 (Cambridge to Caledon, if not all the way back to Collingwood), 28 (Port Hope-Highway 115), 33, 27, 59, 67 in Timmins, 86, and 121 between Minden and Haliburton to be fully restored. I don't care who maintains them, but a "maintained by ______" tab underneath the highway shield if necessary.
Highway 7 is probably okay through Brampton and York Region without restored signage (though I'd argue it should still continue through to Highway 410 in Brampton from the west, instead of abruptly in Norval), but it should be restored westward to Sarnia.
Many other routes, like Highway 18 south of Windsor, Highway 22 near London, Highway 76 in West Lorne, the southern section of Highway 121 (though Kinmount), Highway 93 between Highway 11 and Highway 400, made sense to download. Highway 11 probably didn't need to exist anymore south of Barrie. But there were too many important through routes and connecting highways that were thrown away without any planning in the Harris fire sale era.
Agreed completely. I think if the former King's Highway serves an important backup route for a 400-series highway (ex: Highway 2 like you mentioned), then it should be continuously signed as such. Ditto for downloaded regional roads that connect 2 sections of still Provincially-signed highways (like Highway 7). I've tried to drive both Highways 2 and 7 for much of their route, and in a lot of cases following the signage is quite difficult, especially when the highway has been upgraded post-download. An example of this is Highway 7 through Guelph and through Brampton. What a mess. As for Highway 17, the only section that isn't signed as such is Highway 174 in Ottawa. Once it hits Prescott-Russell, it becomes 17 again (Provincially signed). I do agree that keeping the stubs of highways within urban areas signed as Provincial highways (ex: Highway 11 in Toronto) may be a bit redundant though.
Ideally, I'd like to see all of Highways 2, 3, 7, and 9 restored to Provincial signage, even if the maintenance remains with the municipalities.