I am currently becoming very interested in the Indian railway scene. Once my current US project is finished I'm seriously considering doing a route based on the sub-continent.
With David Drake releasing the DHR buildings etc. on to the DLS there are plenty of items to give the unique character and of course many of the existing built in items can serve as background scenery.
The biggest challenges are...
1. Where to start! There are so many diverse and scenic routes, but my current shortlist is looking something like this:
NE Frontier Railway from Lumding to Haflong and Badarpur.
Satpura lines from Jabalpur to Nainpur and Balaghat.
Kangra Valley Railway
Braganza Ghats section from Kulem to Londa Junction - this looks particularly fascinating, most trains seem to stop to take on banking locos for the steep gradients.
2. Obtaining information. I've already bought an old Indian Bradshaw timetable and just ordered the Great Indian Railway Atlas. However detailed (topographic) maps to use in Transdem are hard to find, the best being the old Russian maps albeit some of these only available at 1:200,000. Not all of the country is in high res on Google Maps/Earth and I doubt for a country where railways are regarded as militarily sensitive, there's any hope of getting detailed track plans or gradient profiles. However that's what imagination and improvisation is for!