I'm not sure why AirTran couldn't be the next Eastern, using the strategy ExUsair describes. Southwest has demonstrated pretty conclusively that an airline can be unionized, pay well, have happy workers, AND have low costs and low fares. A low-fare Eastern, with workers who weren't overworked, with 717's to ply the east and National's 757s to ply the transcon routes, that sounds like a winner to me.
And should a "New Eastern" want to go even higher capacity, say for transcon and trunk NE-Florida routes, they could add the 757-300 which has lowest operating costs of any plane, piggybacking on crew and maintenance commonalities with the 752.
But it does require that the carrier remain low-fare. Delta has obviously more than filled in the gap left at ATL without Eastern even with high oligopoly fares. I think "New Eastern" under the above conditions could be a winner. Get the paint stripper and find a hangar.
Need a new airline paint scheme? Better call Saul! (Bass that is)