Good shout but with DTG no longer interested in doing the steam traction that is the primary motive power on this route, unlikely to happen.
I wouldn't sweep the topic off the table so quickly. A few months ago there was a developer in the PC Editor part of the forum called Nexus who wanted to implement the HSB Brockenbahn professionally and was also planning a route from Magdeburg to Thale in the Harz. Since then it has been quiet and the Magdeburg-Thale implementation for the TSW Editor has been cancelled. But I can well imagine that we will hear something from Nexus again in the future, as the HSB is said to have agreed to a license release. So wait and see and keep playing TSW5 in the meantime, something might finally happen on the topic of steam locomotives for TSW too.
Tourist railways are a good idea. This is one that I would like to see. It's a pity that DTG isn't doing any more steam routes and locos any time in the forseeable future. We should get more steam trains.