As described above, Toole read Waugh, especially Brideshead Revisited. Beyond the theme of ritual scapegoat, Confederacy shares other themes with Brideshead. For example, Waugh plays with the theme of homosexuality (bk 1 chap 2) and its relation to the medieval and renaissance Neoplatonic ideas that love for another human is a foretaste of human love for God (bk 2 chap 4). Confederacy plays with roughly the same connection between homosexuality and love of ones fellow man in the "Save the World Through Degeneracy" campaign. See my paper "The Dialectic of American Humanism" regarding Toole's use of Ficino and Neoplatonism.
I have tried to find a literary study of Brideshead from prior to 1961 (when Toole started planning Confederacy) that discusses the Neoplatonic elements of Brideshead, and I have not found it. So one cannot point to a critical text as a possible inspiration to Toole to use Neoplatonism in his own novel. I have found the Stopp book, Evelyn Waugh: Portrait of the Artist (Princeton, 1958), to be useful. A more recent study that does discuss the Neoplatonic elements of Brideshead is the book by Robert M. Davis called Brideshead Revisited: the Past Redeemed (Boston: Twayne, 1990).
One huge difference between Waugh and Toole is that Waugh embraced Neoplatonism, while Toole critiqued it by making Ignatius a Carnival version of Ficino's philosophy. In his book The Creative Element (Hamish Hamilton, 1953), Stephen Spender examines Brideshead in chapter 9. He argues that the main character, Ryder, is ultimately shallow. The essay ends, "It is when [Waugh] identifies his prejudices with a moralizing religion that qualities anachronistic and absurd in his view of life--intolerance, bigotry, and self-righteousness--work against his talent, and even tend to caricature the very ideas he is supposed to be supporting" (174) Toole could have been aware of the contents of Spender's essay.
Thesis: Discuss the Neoplatonic aspects of both Confederacy of Dunces and Brideshead Revisited. Include a comparison of their approaches to Neoplatonism and homosexuality.