Some Quality of Life Ideas

Water function on Boiler - Every (you pick time) the water will run out inside the boiler so the water has to be refilled after a certain time, it leads to the construction of Water Towers along the Railway
A Subway Train - Consists of the Main Car which has the Control Part or whatever you calm them, and a few seats. And the Car of course for more seats
Coupling Hook - for both coupling and uncoupling Cars
Switch Track - Add a version of the switch track where it doesn't have a lever on the block itself, rather when with redstone it is connected so 2 switches don't look weird.
Switch Track Hook - Whenever the Switch track doesn't have an actual switch the driver can hold a hook that can change the tracks.
Mail Car
Fish Car
Barrell Car - Could Load up things in a barrell like Fruits, etc.
Passenger Unloading - A way to unload non-player passengers (Villager, Piglin, etc.) without having to destroy the passenger car.
Signal Man's Flag - Certain meanings like Red for Stop, Green for Go, etc. A way to raise it is by holding Right Click.
Rail Intersection - New type of Rail
Looking forward to see one of these suggestions get added in the future, i hope.