Introducing a constitutional amendment:
Changing our Capitol AmendmentThe following changes will be made to the Southern Constitution, Article I, Section 2:
2. The regional capital for The South established in this Constitution shall be Nashville, Tennessee Austin, Texas. The region may also be referred to as the Southern Region.
If it must be changed (and I can definitely see a case for doing so, mostly because Nashville is a sh!t city), it should be changed to something like New Orleans, Memphis, or Atlanta. Can Austin even be described as a Southern city, at least to the same degree as the ones mentioned.
EDIT: Another possibility is to have the capital change seasonally. New Orleans for winter, Austin for fall, St. Louis for summer, and Atlanta for spring would cover pretty much all major regional divisions of the South, as well as avoid extreme weather.