As I understand it, the more direct routes from Chicago to Florida, via Cincinnati, Kentucky and through eastern Tennessee (Nashville or Knoxville) to Atlanta are in very bad shape and very twisty and indirect that it would be much slower than the better maintained route of the Cap and the Silvers, which already have passenger infrastructure (stations and platforms and places for any needed servicing.) It would cost many millions, possibly billions to upgrade the tracks along any of the Atlanta routes to even 60 mph, let alone near high speed rail, and the routes are so convoluted, the times would still be dreadful.
The rumored Chicago<->Florida service is just a matter of scheduling, no construction required.
Maybe if successful, a more direct route could be pieced together from various future corridor expansions and upgrades (Ohio's Cleveland, Columbus and Cincinnati service, Atlanta commuter rail to the north, etc.) because the corridor projects would have filled in and upgraded some of the gaps.
The idea of 24 hour + layover in Washington makes no sense at all. If that were the plan, they could just change the Cap from Superliners to Viewliners/Amfleet on the existing schedule, and move the Superliners to the western trains. No fuss, no bother, and no reason for AU to get involved except the traditional second-guessing of everything Amtrak does.