The Emerald Night is an excellent starting point. Perhaps once you develop a single passenger car for the Polar Express, other LUG members can make additional passenger cars. Each passenger car might need as many as 18 train windows and 2 train doors. Looks like it will be drafty inside my Hogwart’s Express and red soccer bus for awhile.
I like the idea of using it because it has the working pistons on the wheels and it is not an insanely large locomotive. I think it could be adapted fairly easily to make a Polar Express that would be identifiable by the general public (but probably decried by trainheads – oh well).
Let’s make the train doors white! I think I know where we can get a few white doors! 😀