OK this one is a pet peeve of mine. When you complete a task you get a little beep as an audio acknowledgement. I'd love for one to be put in for when you're at a station stop or waiting departure time and you get the acknowledgement to close the doors, I know full well I'm not the only player to be on your phone or reading or making a brew etc etc while the train is at a stop and you miss the instruction to close the doors thereby making your train late.
This would be very handy for driving without the HUD. I've disabled the 'task completed' sound because it is unrealistic, but a bell that rings or the like as if a train chef has given an 'all doors clear' sign would not be unrealistic and would aid in drving HUD-less.
There used to be a mod, but since TSW3 there is a setting in the settings > Audio menu, called 'in Game notifications'. Settings this volume slider to 0 disables the objective sounds.