That fits some of my speculation. I been wondering if a relative of Tommy's is a villain, meaning the Merlyn of the comics.
Never thought it would be the as yet unnamed "Well Dressed Man". But that would explain a LOT! The mystery of the name, any DC villain would not have much need to keep it secret. It being Merlyn would would explain the secrecy of the name. Its partially because of the comic character but more about the show itself. Where Oliver is a friend of his son.
I liked this episode a lot. Oliver needed Diggle in a the secret. It gives him someone to talk to. Was there as much narration as before? Seemed like less. He fills the classic role of the hero explaining things to a partner. Which gives insight into the hero. Like Dr Watson, Robin, Alfred. Also Stephen Amell has really grown on me. He seems to be bringing more depth to the character. The scene of him on the island with the vision of his father was very effective.