My feedback is "Thank you." With all the talk about AI decompiling and reverse engineering I see daily (Pokémon just yesterday), I had the idea of coming to this forum and I'm glad I see someone making some strides.
I think fixing little annoying things will be a big improvement. I haven't played for 2 years but off the top of my head:
Each 45° turn has the effect of 2% grade when it should be 0.5% at most for any curve, no matter how close together they are.
The fact that trains obstruct intersections feels excessive. Same for broken down trains.
Is it true the economic cycle follows your personal situation in order to harm you? I couldn't believe it when I first read it but with time found it more convincing.
A second station in the same city/industry creates its own demand. Silly!
Irregular production rates.
I don't have a big imagination so I will leave new features proposals to others. What Jeffry said about fleet management (or just the auto renewal of locomotives) sounds great.