Small Sternwheeled River Paddle Steamer
It uses somewhere just below 1000 pieces. Estimated cost I believe would be around 70$, but I'm not sure about that.
If I had chosen to make a sternwheeler of a perhaps more recognizable, larger type, those with three or more decks and two smoke stacks, then I think it would have become too big to be a viable set. But there are a few prototypes that look pretty much like this. Most of those prototypes seem to be quite modernly diesel powered though, but this model of mine is steam powered!
The possible set would include, at a minimum, around four mini figures: two crew members and two passengers. Mini figures are about the most expensive types of parts for Lego to produce, so we will have to keep the number down somewhat.
Apart from the touristy city figures used here, this could be outfitted with several different themes as regards the minifigures, like Adventurers, Indiana Jones, or perhaps, as someone suggested, an American Civil War theme...?
To support this paddle steamer to be made into a real Lego set, first get an account here, then click the Support button on the upper right side! You will be asked how much you would be willing to pay for the set -- that does not mean that you in some way agree to actually buying the set when or if it comes out!
The steam engine workings can be checked out nicely since the whole port side of the ship is hinged and can be folded out like this! Here you can also see the long steam pipe that leads from the central boiler to the two cylinders in the stern. Even though it cannot be seen clearly in this picture, one of the cylinders, the one where steam enters first, is larger than the other.
You can also see the steering cabin, the small cafeteria in the stem, the coal box, a shovel on the wall, the luggage compartment, and a small crew area with a table beside the cylinders in the stern. The passengers have their main area on the upper sun deck.
Here is an image from the stern, which shows the paddle wheel clearly. There are working pistons which move back and forth if the paddle wheel is turned. The hexagonal pieces used here were invented quite recently by Lego, originally for use in a combine harvester!
As you can see here, there are small bulbs in the bottom of the hull so that the ship can be pushed on the floor or a table without leaving ugly marks; this should increase playability.
As an extra gimmick, the paddle wheel could be "motorized", like shown here. This uses no actual motor, but a rubber tire wheel which rolls along when the boat is pushed forward, drives a chain which makes the paddle wheel turn as the boat is pushed.
You may also want to check out the MOCPages page of this! MOCPages is a site where people display their own Lego creations like this one. There you can click your way to bigger pictures of the ship, and also get the MLCad .mpd file, which is a "Lego CAD" computer drawing of this boat, which can be used as building instructions and for many other purposes.
Please also check out my other Cuusoo project, a small trawler!
Have a nice day!