Yes, Elvis would be amazing. There's actually REAL country artists I want too like Waylon Jennings, hell even his son would be nice (He's borderline southern rock/country). Or Johnny Cash, but I don't know how much excitement doing anything but vocals you'd get out of it.
Oh, let's add some blues players while we're at it too, like Muddy Waters and B.B. King. or even T Bone Walker.