Just wondering how you got on with the project?
I have decided to build a Discworld railway based on raising steam. (not sure I can build the goblin underground that would be a challenge!!!)
My New Ankh Station (I am going to base that on one of the London terminals possibly an older St Pancras), the layout by chance I came up with was similar to yours but missed out the river (Will add)
I intend to run two lines as a ring. the will run right towards Quirm, then a tunnel possibly with Lancre and hub mountains painted on it with the return line via The sto plains. I will have a couple of trains running around those loops.
Key things for me is for it to be discworld theme but not reproduced 100% accurate, aim for it to be fun railway to build and run.