It always dawned on me that the trains in Rail Nation aren't too realistic and that there's a lot or confusing and contradictive information in the trains and tech tree.
The eras are also confusing, as era 1 and 2 are exclusively steam engines, era 3 and 4 are exclusively diesel engines, era 5 and 6 are exclusively electric engines. I believe this should be remade to instead go by time periods. Because the E 94 nicknamed the "German crocodile" also known as the Leviathan which is a Era 5 electric engine were made in 1940. While that the Deutsche Reichsbahn also known as the Lynx which is a very popular Era 2 steam engine was made in 1960 which seems very contradictive.
While that I love the idea of having different skins for the same engine type, it can cause confusion because the Class A4 Mallard is the fastest steam locomotive with a record of 202.58 km/h but it's only used as a production series for the Boar which has a top speed of 130 km/h.
In my opinion the tech tree should be redone to have more engines to choose from and more logical production series and at the same time changing the eras in the tech tree to be more focused on time periods then type of engines.
And in addition there should be trains that can used as both cargo trains and passenger trains, especially steam engines.
To conclude a new server type would be in order to make all these changes and not to anger those who love the way the game is currently, the tech tree eras should be remade to go more by time periods then engine type, and the tech tree should include a larger variety of engines.