Liam is just born for the mentor type of roles. Im so glad Nolan didnt think casting Liam as mentor would be a lazy and obvious casting because of his Qui Gon Jinn role. I really think what actors played before is irrelevant and shouldnt be in the way if the actor feels right for the role, wheter he played the same characters a million time or none at all
Well, I never even had a thought of him being supernatural coming through my mind, but he was very interesting character nonetheless. We know that he also has been through great pain, and we see what his loss did to him and what kind of devotion and obsession against criminals it caused in him
I dont think there was any ambiguity there about his immortality. We know Nolan was going for realism and so supernatural was out of question. Then theres the script which describes Bruce as realizing Ra's true scheme, which is passing the Ras name from leader to leader. And then theres Ducard's story of his wife, I dont think supernaturality is hinted there in any way

