All of this is fascinating. I look forward to reading Professor Thompson's book.
I am sure he knows of the neglected short book by William E. Dodd: ROBERT J WALKER: IMPERIALIST (1914). (Dodd of course became FDR's first ambassador to Nazi Germany and was Howard K. Beale's undergraduate teacher. Beale developed the once famous Beale thesis that gave an economic interpretation of Reconstruction. Beale in turn was C. Vann Woodward's teacher.)