I like your idea. I agree that producing a diorama that depicts an active railroad setting is a challenge (unless you’re satisfied with a loading dock scene. - boring!). That said, I can’t see shifting the theme of this project in that manor.
As for the abandoned tunnel, I actually contemplated including a mass of fallen rock, behind the fencing, to add to the depiction of abandonment. I added the signage to emphasize it’s sorry state.
Thanks for the feedback and the suggestions. (And I will be adding smoke staining to the portal.)
Ralph