https://www.railway.supply/en/georgia-moves-ahead-with-atlanta-to-savannah-rail-line-study/
IMO the route is just too slow for a reasonable trip time the Nancy Hanks on the C of GA took almost 5 hours ATL - SAV. That does not mean an Amtrak would necessary take some route especially ATL - Macon.
It looks like there are three routes one using a new ROW.
What about NS to Macon and onward on the short line(s), upgraded to 125?