This is The Polar Express!

Most of the parts I needed arrived. So here's a mock up of the Passenger Car with conversion to Observation Car!

The rear "end caps" are easily interchangeable using pin connectors.

I chose sand blue and dark red for the colors and maintained a 6-stud width for the body of the car. Now I'm waiting for some dark red door windows to arrive.

The set would include the following:

1 engine, 1 tender, 1 passenger car with interchangeable end caps, 3 minfigs, track, and basic Power Functions with lights.

Upgrading to a rechargeable battery and ac adapter are recommended.

Between the book and the movie, the common characters are the boy, the conductor, Santa, and the hot chocolate servers. So I figure I'd at least want the boy (in yellow pajamas and blue robe), conductor (with a blue hat), and Santa included in this set to stay true to the book.