I don't see how a credible list could ever have been made. There were many Unionists in the South who fought for the Confederacy and many who tried to be neutral. I know of a Unionist slave owner in Texas who was a prominent judge and too old for conscription. His three oldest sons served in the CSA and two of them died at Camp Douglas. He had a son-in-law who served in the Army of Northern VA and the two of them remained close friends for the rest of their lives.