HWA was not the only one to talk about this throne. Back in medieval times it was taught by some associated with the Franciscans that St. Francis of Assisi was destined to sit on Lucifer's throne. The following quote is from a 13th Century book entitled The Assisi Compilation promoting the Franciscan Order.
Here Francis and another monk, Pacifico, are described as being on a journey and stopped to spend the night at a church. While praying Pacifico is described as having the following vision.
Brother Pacifico was taken up in an ecstasy, whether in the body or out of the body, God knows, and he saw many thrones in heaven, one of them higher than the others, glorious, resplendent with every precious stone. As he admired its beauty, he began to wonder what kind of throne it was and whose it might be. All at once he heard a voice telling him, "This was Lucifer's throne and blessed Francis will sit on it in his place." (The Assisi Compilation, section 68, in Regis J. Armstrong, Francis of Assisi - The Founder: Early Documents, vol. 2, 2000, p. 168.)However, unlike Armstrongism, there was no mention of this throne being connected with authority over the Earth.