Of course you can pause, but that means everything stops moving. The OP’s point is that everything should move at the same speed it currently does, but days should pass less quickly, so a year takes longer, and each train fits in more journeys in the same span of time.
As the economy is fairly finely balanced around the current speeds, I think this could work if you not only doubled the length of days, but correspondingly halved the revenues, running costs, maintenance costs, etc, so that at the end of a year, everything had completed twice the number of journeys, but had made/lost the same relative amount of money in the process.
It could then do with an 8x time speedup option, so that you can accelerate time to the same degree as before.
Maybe go a step further, and have an option to quarter everything, have 4x longer years, and have an additional 16x speedup option.
The problem with the speedup stuff is that it could push the game beyond what most people’s CPU’s can handle… but then again, this would all only be an optional choice when you start a new game. It could be labelled “requires a powerful CPU to use faster time speedup”.