I've been wrestling with the question of how to manage the F&B situation on long(er)-distance trains. The best that I can come up with is some sort of "A-train"/"B-train" division:
A-Train: Operates with a full dining car and a separate cafe car, CCC, or SSL.
B-Train: Operates with an "enhanced cafe"/"diner-club" car. I'm thinking that this should generally be either (1) a single-level diner, but with only two OBS (a cook and an LSA) serving a menu including some full entrees (sorry, but a caesar salad or a panini doesn't count here).
Ideally, you'd have an A-train on most (if not all) LD routings alongside a B-train, with a difference in sleeper fares (and possibly a smaller one in coach fares over longer distances). We don't live in an ideal world, but this is what I'd shoot for. I'd also shoot for a LOT more sleeper space across the board (ideally most single-level LD trains would have no less than four sleepers outside of slow seasons), albeit at slightly lower fares than we're used to. I'd also shoot to make the really long-haul day trains (Adirondack, Palmetto, etc.) into B-Trains as an upgrade of their cafe-only status. The Adirondack in particular is really galling in this respect given the amount of end-to-end traffic on that train.
Realistically, something like this could only be done in the East: The demand appears to be there for a second LSL, and there's plenty of precedent for three daily trains NYP-MIA (if not the equipment right now). The Cap-Pennsylvanian operation would be a hybrid, and a re-extended Pennsylvanian could easily operate as a B-train CHI-PGH (alongside the Cap as an A-train). Worth noting is the fact that if you're willing to exchange equipment between trains (and sacrifice a bit of utilization optimization) you could have the "base sets" switch between the A-train and B-train while the "premium" equipment stays with the A-train. The best comparison at present would be the extra sleeper on the Meteor (the third sleeper and its attendant stay with the Meteor both ways while the rest of the crew alternates). West of Chicago, the only plausible routes for something like this are really fragments of the Zephyr, Builder, and possibly the Starlight as a whole.
There's one other option, which would be to disentangle the "included meals" line on most trains. Doing so would probably allow you to get another good chunk of capacity on the train before overwhelming the diner (e.g. 5-6 sleepers on one diner instead of a practical limit around 4 right now). I've mulled over ways to manage this, but a fair point to be had is that if you have more sleeper passengers per train there's a corresponding decrease in the number of times that diner service demands will behave oddly on a given run.