Sounds nice @snowball, I also wrote some weeks ago, but never heard back something.
I now started to create my own map ("Berner Oberland" / "Bernese Oberland"), a bit bigger than this area so its size is not a 1:1 to the real world. (just published yesterday on steam workshop). Its huge and has a lot of towns. (maybe too much )
It was a lot of work still, to make the heightmap, placing the cities and industries (because the tools are buggy or it doesn't work nicely with the heights (I used 4000 to make it look more real including some snow up there).
However it helped me to get a bit into it how to make such maps.
So I will have less time in December than now, but I would be still interested in joining a team to make something.
I liked the "Gotthard" Mission how this was building the tunnel when you took away stones, in the Jungfrau region there might be similar possibilties with the Jungfraubahn through the Eiger, but probably not with trains (rather tram), because trains can't be built steep.
I am wondering if there is not a possibility to make trains also work in more steep scenarios, but could not found any mod yet.