I've heard "Devil's Plant" works well as an eggplant rootstock. We have a native solanum here in Oz called Kangaroo Apple, and I've also heard of those being used. Also got a thriving Rocoto, which I'll try. We're not great eggplant fans, but we love out of season capsicums and tomatoes.
Here in Melbourne we're 38 degrees south, which is equivalent to the Carolinas (I think), but with scorching summers. It's our sprnig now, so we will definitely give this grafting solanums a try, and may be able to report back before the northern spring.