Just because a DMU could be setup for sleeping, doesn't mean it should. First of all it would be the only sleeping DMU in the country, so the utilization of the required spare train would be very low. Secondly, DMUs tend to only be beneficial for short 1 or 2 car trains. At 3 cars they are a toss up and at 4 or more cars, a conventional train is more economical. A sleeper train needs at least 1 baggage car, 1 coach car, 1 dinning car and 1 sleeper, so you are at 4 cars and you haven't added any for excess capacity. If you look at the following video of a train entering Churchill, it has 7 cars, so it is no where close to the size a DMU would be beneficial.
So, as I see it, any non sleeper, under 4 car train could be DMU. That could not only include Sarnia - London, Sudbury - White River, Montreal- Jonquière, and Montreal - Senneterre, but also Toronto- Kington, Ottawa Kingston and Montreal Kingston after HFR is built. There will likely be a need for service, but not at the current amount. This would give an easy way to upgrade those sections served by RDCs and short trains.
The key phrase in that point is "if it is full." Even if it is full, having double the number of departures isn't a bad thing when service intervals are infrequent?
Agreed. I'll bet there is a number of seats needed filled to be considered successful.
I agree it isn't a simple. There are many factors, some you like to highlight, and some you like to ignore.
I don't ignore them. If anything, I look into why those factors exist and what can be done to mitigate them. The Northlander is a great example of this. I don't ignore all the reasons it shouldn't come back. I try to figure out how to resolve them.