I don't, but I'm thinking of writing one too...
It occurred to me that operations (which I haven't got into yet) tend to be described in terms of either huge unit trains, or car cards with destinations and return addresses, or even random arrangements. But surely the movement of freight cars is determined entirely by the industries along the way, and the movement of locomotives is thus determined by the movement of freight cars. Of course, it makes sense to have a way freight or through freight go at a particular time of day, but only once it has been determined that that would be the most efficient and useful route. I would like to think that my (freelance) railroad was going to attempt to make money by keeping customers happy (most of the time), while it can continue to be profitable.
So, starting with a list of industries, freight 'orders' would arrive from customers, and the, erm, 'logistics engineer' (in today's parlance) would organise what was actually happen and when, and advise the despatcher accordingly. Of course, we won't be able to satisfy everyone all of the time -- that's part of the game anyway.
As I get used to operating the schedule efficiently, I can increase the size of the industries (as they increase in size), or build new ones. If it gets too much, well we could always have a bit of a recession...
Anyone else tried this?
Charles