I have only recently started playing MudRunner and enjoy it a lot! What I have always wanted to see in a game seems nearly possible with some of the same basic concepts and some of the same game engine I would suppose, although I don't really know.
A game like .MudRunner but with rivers instead of roads and Barges and Towboats instead of trucks. You would haul coal, oil, wood chips, scrap metal and whatever up and down the inland waterways of America or other continents. A great start would be the Mississipp, Ohio, Tennessee and Tombigby Rivera from Pittsburgh to New Orleans and Mobile to Nashville. Navigation thru loch chambers and river channels. Challenges would include fast high water, hauling cargo tonnage and so on.
Maybe I'm crazy and the only one who has ever thought this would be fun?