There may be a few local stops that are questionable, but we don't need to set up a provincial milk run network to serve Strathroy, Wyoming, Ingersoll, St Mary's, Trenton Jct and Gananoque. VIA's current solution - only stop once or twice a day in these places - is sound and positions things for growing the ridership.
Not sure I agree, looking at this from an efficient business perspective.
An efficient business ensures that it operates where marginal costs equal marginal benefits. To equate this to what we're talking about here, think of serving a smaller intermediate community (e.g. Strathroy, Wyoming, Ingersoll, St Mary's etc.) as a cost; the time spent accelerating/decelerating and dwelling at the station is extra trip time, extra time that may make the service unattractive to someone commuting between two major cities (and therefore is lost revenue i.e. an opportunity cost). The benefit of serving a smaller intermediate community is that you gain additional revenue from picking up additional passengers.
Remember that the opportunity cost for one lost passenger between two major points is greater than the additional revenue from gaining an additional passenger at an intermediate stop. So in essence, you would need to pick up more than one passenger at the intermediate station for every passenger lost at a major station.
Now I'm not arguing whether the marginal revenue at any particular station is worth the opportunity cost. But cumulatively, I'm willing to bet that there are collections of intermediate stations between Windsor, London, K-W, and Aldershot, as well as Oshawa, Kingston/Belleville, Ottawa and Montreal where it doesn't make economical sense. Same goes for other parts of the existing VIA network where this parallel can be reasonably drawn.
I'm also arguing this against the backdrop of operating costs. I think we can agree that VIA, in the way it currently does business, has greater operating costs per passenger per kilometre than a provincial service (bi-lingual compensation, on-board amenities like food, employees per passenger). So a rhetorical question: is it more economically sustainable to operate a milk run with a higher cost premium service, or a lower cost provincial service?
This is not a blanket argument for all parts of Canada, but it is an argument for low-hanging fruit; markets that are denser and with established rail corridors and no provincial service (e.g. southwestern Ontario).