Frankly I think the Slumbercoaches would run into ADA problems these days. You're supposed to try to make things as accessible as possible for people with mild disabilities, and that design, yeeowch, my fiancee would want nothing to do with it.
The dining car? There's no reason in the world why it couldn't run pretty much the way it did then. By all accounts the serving procedure was actually *more* efficient than today's is. You just need high volumes on the train to get the high turnover to support the fixed costs.
The losses cited were about $6m/yr ($20-24m in 2013, depending on your measure). Per the measuring of the graph Boardman put in that testimony to Congress, the Crescent now runs with a direct loss in the range of about $7m/yr if I'm not mistaken...and most of that loss can probably be found south of Atlanta. The Crescent was, I believe, tri-weekly BHM-NOL at the time.
I've been fiddling around with a spreadsheet relating to the direct losses. We know that the Auto Train, Palmetto, and Silver Meteor are already profitable on direct costs. It looks like ordinary growth over a few years (5% total, perhaps) should get the Silver Star and the Lake Shore Limited to the same status.
The Cardinal has an obvious problem; it's three-a-week. After correcting that and getting the proportional revenue and cost changes, it looks like it would need a slightly more substantial additional growth in revenue (maybe 10% total) to achieve the same status. This would probably happen; revenue growth when going from three-a-week to daily is generally *more* than the 7:4 ratio of frequency, due to greater convenience.
The Crescent would need more improvement than that; it seems clear that it is bifurcated into north-of-Atlanta and south-of-Atlanta markets, and that cut-off cars at Atlanta are badly needed. In the PIP in 2011, based on 2010 numbers, this was estimated to save $0.3 million in costs and increase revenues by $1.2 million. (The lounge and two or three coaches would have been detached at Atlanta, with a coach added north of Atlanta.) But ticket prices are up (north of Atlanta anyway!) -- Crescent revenues overall are up by 10% since then, so we can probably estimate it to be worth at least $1.32 million in revenue now (the PIPs generally lowballed their revenue increase estimates). With new Viewliners, another sleeper could be added north of Atlanta only, and this would probably be worth at least another half million, probably much more.
Anyway, I figure that if the Crescent gets a new Atlanta station which isn't overcrowded (allowing more passengers), and where it is possible to store rolling stock overnight, then the Crescent could probably achieve the same profitable-before-overhead status. But unfortunately a new Atlanta station seems to be unlikely to happen in any reasonable timeframe.