I wonder what the significance of "Journey to the Centre of Arcanum" was, in its original context. Did the Arcanum sequel that had only just begun before it was cut down feature a Jules Verne type plot? Perhaps we might have seen more ancient Vendigrothian submersibles as well? It seems to be an extension of the literature of roughly the same period as Arcanum, although the reference to the famous author's work is from a slightly earlier period. However, the genre as a whole extends quite past Arcanum's period. What does everyone think about this? What I want to know is, why journey to Arcanum's core? Are you chasing someone, or looking for a secret, or perhaps fleeing?
The project never took from the drawing board, but your guesses look solid. Driving around in huge Vendigrothian submarines in the HL2 engine would have been a blast. My guess is that the storyline would begin as a scientific research expedition ordered by the University of Tarant. Of course, once inside Arcanum's core things quickly go grim.