What happens when the number of people wanting to get off the train exceeds the available limit of the intermediary vehicle? They'd either have to be really big or tailored per journey based on the tickets sold for that trip, with the addition of any open tickets.
Also all the really boring technical "That's impossible" talk from everyone else: He's not an engineer, but you throw enough money at a problem and they'll give you a solution).
PS: What colour would it be? I suggest silver, like a fox ^^