O.k. If I put my name in the hat, I need to start my build log. After checking in with my assistants (my 11 yr old son and my wife), I think we have come up with (at least) a start of a design.
I will do a mini-ferris wheel with a pully or gears connected to the truck wheel(s) to have it turn as the flat car is pulled around the track. And, maybe, I might do something musical with a player piano or music box type of thing - again connected to a pulley or something (kind of like the Rube Goldberg theme).
Now I’ll have to under promise and try to over deliver (boomer has me shakin in my boots now - har-har).