Since Lukas already leaked some of our planned features in the TrainSimPlay interview (in German) I might as well list them here

1. Realistic coupling procedures with the ability to manually connect individual hoses and open/close angle cocks.
2. Brake heating and ice physics simulation (with the possibility of almost entirely losing brake force on an iced over brake shoe, requiring manually removing the ice, or overheating the brake shoes to the point of melting them if you get stuck brakes for example).
3. Air leaks that you need to identify as part of the train preparation (brake test) and that could necessitate cutting out the brakes on the affected wagon.
I don't want to spoil too much (and a lot of this is still heavily WIP) but I guess what I'd like to convey is that a lot of these features are meant (in addition to simply increasing realism and attempting to get as close to reality as possible) make things like brake tests and train preparation actually have consequences if you do them, or if you skip them

There are some other features I'm working on that I'm really excited about, but they are quite ambitious so I can't talk about them yet (I'm not 100% confident I will be successful).