I really love how y-lands has implemented the small steam engines, and ylandium engines into the game. When I first heard of the steam engine concept of the game, my brain shot directly to steam locomotives and railroads, along with your antique riverboat. A steam powered car didn't really come to mind. Not to say that a steam powered car was never a thing, but that's besides the point. I think a great use of the steam engine would be in the case of a steam locomotive. Perhaps make rails craftable with planks and iron. If you were to utilize the same foundation of the ships and cars, where players can craft a chassis, or a basic ship that can be built onto, players could create extensive railroad systems to transport items around while building onto a basic rail car.
Not sure if anyone would be interested in this, because the islands are somewhat small for a railroad, but I think the idea would be pretty cool.