I think it is a solution to a non-problem, to be honest.
If you only get mail two days a week, you don't have a letter carrier walking up to your front door with empty mailbags the other three days. We have a route measurement system that accounts for fluctuation in mail volumes, and Canada Post is very well situated to adapt to that. Over the last 10 years, as letter mail has begun to decline, the number of letter carriers has declined by the same percentage. That's already built in. If you only get a letter once a week, you only have a letter carrier coming to your door once a week.
Some people get mail five days a week and they rely on that, but if you break the delivery model where they deliver the parcels and letters together, it will become a lot more costly. They can save a lot of money...because what it would mean is you'd have basically two people going up the street every day. In that sense, it makes it more environmentally friendly to deliver.... Actually, Canada Post delivers parcels with the lowest carbon footprint in the industry. They do that precisely because they are able to combine this work and combine efficiencies. That's on a financial scale, but also on an environmental scale and others.