I would advocate the splitting of the Sunset Limited as well at New Orleans, for the main purpose of improving timekeeping so that trains will depart NOL on time. However the drawback is misconnects should the western train get into NOL after the eastern train departs, or vice versa. I think the number of through passengers at NOL is not all that great. And the long dwells built into the schedule to accomodate the padded schedules necessary in each direction are also unattractive should the train be operating on or close to schedule.
Besides, those going from the eastbound Sunset to the northbound Crescent already have to stay overnight, and same thing southbound Crescent to westbound Sunset. I could think of a lot worse places to have to spend the night than New Orleans, which has a vibrant nightlife.
Overall, yes the Sunset should be made daily, and that includes both sections of it should it be split into two separate trains.
Perhaps the eastern Sunset, redesignated as the Gulf Coast Limited, could have its schedule flipped, so that it leaves New Orleans in the morning, serves the casino market at Gulfport & Biloxi at a decent time, and gets to Jacksonville in the evening. Then by extending it to Miami, and running it slowly, you can offer an overnight trip between Jacksonville and Miami. Currrent travel time is now about 9 hours, so even without a highly padded timetable there would be more than enough time to sleep before a morning arrival in Miami. Same goes for the other direction, late evening Miami departure, morning stop in JAX, and then daytime travel JAX-NOL.
The CARDINAL should be retained, in my opinion, and by all means it should run daily. While it does serve the Chicago-Washington market just like the Capitol Limited, it serves a very different area. Only the endpoint cities are the same. Relatively few people ride the Cardinal end-to-end, save for railfans like us and retirees who have time on their hands. There are many sub-markets served by that train, such as Washington DC to West Virginia, West Virginia to Chicago, Cincinnati to Chicago, Washington DC to Indianapolis. For those using the train at intermediate points, it's a vital link that can only be made more attractive by daily service. For this reason, calling times need to be improved as well, although there is not much one can do with the horrible overnight station stops in Indianapolis & Cincinnati to maintain transfers with other Amtrak trains in Washington and Chicago.