I don't know with the proposed budget that this should be called a "Fantasy Thread" or not. I believe the extension does have support.
My assumption is the train would split off the Crescent at Meridian, MS and then head to the Dallas/Ft. Worth area. If you go by the current Thruway bus route between Meridian and Dallas (8219/8220) it would serve Jackson, MS (currently on CONO) and Shreveport, LA (no Amtrak train service). The advantage to me would be a one seat ride between the NEC (and the Carolinas and Atlanta) and the Dallas area (what other potential stops do you see?)
If the train can be scheduled to allow transfers to the TE at DAL it can allow traffic from the NEC another possible route to Arizona/California and a route from the Carolinas and Atlanta to Arizona/California without having to travel north to NEC-Chicago or staying overnight in NOL. The train could add a significant number of passengers to the Sunset Limited/Texas Eagle west of SAS. Maybe it helps "save" the train.
One potential problem: Does Dallas (or Ft. Worth) have the service facilities for a LD train (or would it be like BOS or Portland)? You might have to run the train to San Antonio then along the TE route (although I can already hear Bob Dylan saying "they will never allow it!")
Also, if you use the schedule of the Thruway bus it takes 11-12 hours between Meridian and Dallas. The westbound schedule requires a nearly 5 hour wait in Meridian (not a place I would want to spend 5 hr) and arrives in Dallas at 5:50am. If you cut the 5 hour gap to 2 hours and use the same timing, you arrive in Dallas at 2:50am, pretty close to the absolute worst time possible (not to mention you would have to open the station at that hour). For a feasible train to arrive in DAL, you'd probably have to make it by midnight. Can you get from Meridian to Dallas in 9 hours or less, including the time required for the split which will surely count for 1-2 hours of that time? Maybe you can help by shifting the Crescent schedule to leave NYP and arrive/leave in ATL an hour earlier and you'd have a chance to make it to Dallas before midnight.
The other possibility is to pad the schedule so much it arrives in Dallas after 6am although that adds to the travel time and you'd probably have to idle somewhere in the middle (and spending any significant time waiting in Mississippi cannot be good). An early morning arrival (6-9am) into Dallas would shorten the gap between the "Crescent Star" and the Texas Eagle though. If it arrived in Dallas before midnight, the transfer there would be almost useless as it would require an overnight stay (and if you get to Dallas at that time you wouldn't get to your hotel until after midnight, assuming the train is on time, laughs from AU members).