Supposedly bowls don't like to do rematches. The few that have been rematches are usually BCS games (Bama-LSU in the BCS Title game last year, Miami-FSU in the '04 Orange Bowl, FSU-Florida in the "94 Sugar bowl). I don't see why the Chick Fil A bowl would't want Clemson-SCar. Both schools would sell out the allotment, it would be extremely intense, and while we all hate how our game with SCar ended, it was a pretty close game. All kinds of ways to hype it up, too. ESPN can hype up the rematch angle for Clemson, and then do their typical SEC hype with SCar. I feel like there is no downside in doing a Clemson-SCar rematch for the Chick Fil A bowl, Atlanta, or ESPN.
It's not necessarily ideal for Atlanta, because with both schools being so close, there will be fewer people staying multiple days in the hotels, eating in the restaurants and drinking in the bars -- a lot more day-trippers. Obviously, the game would be a sellout, but the economic benefit to the city would be less.