In a perfect world - for the LD trains you'd have regular coach class, then the some sort of service between coach and sleeper. Three classes of service on the LD trains. Slumbercoach would fit that bill well now. Perhaps it faded out of favor by the 1990s (or faded out as the slumbercoach passenger cars were aged out and retired!), but I think it would be a BIG hit now days. Europe has the re-surgence of sleeper trains once again and offer various service levels. Amtrak does not. The Amtrak sleeper cars right now are priced WAY too high - again largely due to the supply/demand imbalance going on right now as a result of parking and not maintaining various passenger cars during COVID. The Slumbercoach was always a cheaper option - providing a compact yet still some sort of bed option. Even the airlines have made strides to create the first class "slumber" seat (flat) arrangement - sleeper pods! If they can do it on airplanes, it could done on passenger trains. Amtrak management is just not there right now. Amtrak is still trying to hire back a labor force and add back capacity too. This means servicing and having folks work on restoring Amtrak passenger cars back to service on corridor and LD trains. But I think a "slumbercoach option for the 21st century" is over due!