As for the larger Airline seats that fully recline into beds, I'm not as sure about that. Would that not take up the same amount of space as a compartment? If it uses the same amount of space, than it would, theoretically, cost the same for amtrak as a sleeper. I might not be envisioning this correctly though.
I say bring back the slumbercoaches! I thought they were great , I'm sure it won't happen but I would love to see them again. To me, #66/67 would be perfect for a slumbercoach, as well as other trains.