Hey, I have an idea (which someone on this forum will destroy for a pretty good reason that's currently eluding me)...
If Waffle House can be open 24/7, why can't the dining car? Most restaurants aren't open 24/7, but most restaurants probably don't have passengers entraining & detraining 24 hours a day, like Amtrak does.
First objection: "There's not enough staff!" Certainly true, as a whole. However, 3-4 of those are servers. If the diner was open the whole time the train was running, you wouldn't need 3-4 servers; you could probably get by with 1 or 2. Same thing with cooks.
Second objection: "They need to close to prep for the next meal!" Yet somehow, places like Waffle House manage to be open 24/7. And, considering how few things are "prepped" onboard, how much prep time can they possibly need? Most of their current difficulty in prepwork is probably space-related: figuring out how to prepare meals for 200 in the space the size of a shoebox. If they could spread the meals out, they wouldn't need to prep so much.
Benefit #1: They could probably create more made-to-order dishes if they didn't have to prep so many meals at once.
Benefit #2: More revenue from diners who didn't happen to be onboard during the prescribed mealtime, greater chances for PAYING coach pax to secure a reservation.
Benefit #3: with less demand for tables, people could sit with whomever you want. If you want community seating, then go during the busier meal times. If you'd like a nice, quiet meal with your traveling companion(s), go during an off hour.
I'm sure someone will explain why this can't work, but I really like this idea.