What about Rouge Plus (Premium) ? On Rouge routes people seem reluctant to pay for more than the basics so availability of something that costs money more than the preferred pittance should be better.
At least they might have Plus seats (oops I guess they are called Premium Rouge) because it's doubtful they are going to reduce space more with more preferred seats. They've done the math no doubt on the marginal uptake and income on preferred vs selling more of the lousy seats.
You could book earlier and hopefully there's better selection. Or try WS on the same route in Plus which might be less expensive.