So basically the plan would seem to be to service New Orleans, Mobile, and the Mississippi coast with a relatively leisurely train trip as an alternative to driving or bus (given there is apparently no real air).

If you had the high-speed train stop only at Gulfport (xor Biloxi) and maybe at Slidell, with regional service to pick up the small towns in between and take pax to the larger stations where they’d change to the faster train, you may be able to preserve a competitive Mobile to New Orleans time and still catch the intermediate city travelers. (This is a limited version of the airline hub-and-spoke to allow the trains to be faster door-to-door than driving, because if you can’t be better than driving in some obvious and personal way, many people will quite reasonably just drive the 140 miles on their own schedule and terms.)