Concerning railroads' capacity for handling new Floridian/Southwind (or any other) service, a some one-tenth mile long passenger train (four coaches, dinette & sleeper) can often duck into a siding with and even run as a leading section of a trailer express. I've been on even longer, usual-lengthed (diner, lounge, baggage, several sleepers and coaches) passenger trains that have done that! If passengers are really paying the railroads for the service then it is a legitimate form of revenue rail traffic just as are the trailer loads.
Now, having to pay for the dining car and its waiters, chef, cook, steward (rather than the mere steward and waiter for a dinette), numerous grand central stationbound management (instead of onboard, "porter-managers") and a baggage car (each car costs money if the railroads are paid the tariff for running it) runs up the bill for fare-paying passengers if revenue does finance the operation.