I love the game, but there could be many changes to any new game to make it a little better for playability.
Industry: There should be a need for industry to be transported, and it needs to not be so spread out and not use the same stuff all over any given map.
1. Coal should maybe be in a few places and need to be transported to where it is needed (power plants, steel mills, etc)
2. Allow cities to have factories that actually use goods to produce other goods that will then also need to be transported. Coal and iron to a steel mill which produces steel for use in automobile manufacturing etc. On a large map for instance there may only be a few steel mills, one even, which allows for transport of manufactured goods to various regions.
3. Livestock, especially in the early years since in America, as an example, rail was widely used to transport cattle to large cities where it was butchered.
4. transport automobiles to cities around the map and please give us container cars for later years since thats how a vast majority of goods is transported by rail today. In later years change coal and ore cars from gondolas to hopper cars.
There are so many possibilities for transporting freight by rail, and the current game only implements a bare minimum of what is often transported. Often there is little to no reason to set up spur lines to goods since trucks do it just as effectively. Make it so rather than just needing x amount of goods for a city to grow, the city needs x amount of building supplies (lumber, steel, copper wire, etc) as well as x amount of other goods (plastics, electronics, various consumer goods. Some of these would be manufactured in cities around the map, while others would be brought into ports and transported via container cars.
Cities and human freight: right now human freight uses the 20 minute rule, but there is no reason to travel to other cities. Why not have people who desire to travel to certain places. They may need to use rail to travel to another city where they will get on another line that will take them to their destination.
Allow large cities to have smaller towns around them that may grow with the larger city and possibly become suburbs of the larger, allowing the building and usefulness of local tram lines to service the direct area and the outlying towns. A large city may even be a hub of rail travel with different lines connecting at large stations (think grand central station or others like it around the world). For these there may even be multiple levels where the east west lines come into the station at top and north south lines come in below. There should be reasons for connecting cities and towns, namely to meet a demand.
The various needs of people and industries could easily change over time. Gondolas used for transporting recyclable steel to recycling centers, copper popping up, aluminum, etc. As time progresses new industries and manufacturing capabilities begin to appear, but please give some rhyme and reason to raw material placement.
Allow changes to semi trucks. Now a semi always has the same trailer regardless of what it is hauling. Allow tanker trucks etc. I love the current game, but there are so many changes that could be made. Finally, for the love of all that is holy please integrate steam workshop for mods. This allows mod downloading and implementing to be done so much easier.
Please give us larger maps.