For discussion of the issues faced when building a model or layout - how to replicate wood, what glues to use, exactly how much weathering can a Gnat take, a good source of detailing accessories - you get the picture, I'm sure.
I can't help with specifics, but I spent a lot of my free time in 1996/7 exploring the Ping Xi coal lines and their remains. The locomotives, of which I saw four, were all similar but subtly different. There was no identification on them. All had the Chen Yu packaged single cylinder diesel which looked fairly new. I witnessed the last day's operation in October 1997 at the mine near Shih Fen which features in the commonly posted video.
I have seen somewhere on a Taiwan website two examples of a more modern version painted yellow apparently used at a gold mine.