DTG, in the future could you spin off the rolling stock from the routes and sell them as separate Add-ons? For example, I am very interested in the "Megafret" Sffggmrrss wagons, which are present on the railways of many European countries. However I'm not interested in buying the whole GWE package.
The designation of Sffggmrrss is just a UIC code that gives a description of the wagon, there are multiple 'Sffggmrrss' and they are all different wagon designs built by different manufacturers. The FKAs in GWE are a different type to the Megafrets that work in Europe. Whilst they are internationally registered they have never worked in Germany, so they are only appropriate for use on GWE.
It might sound a bit greedy from me, but I would like vagons, coaches and AI versions of engines to be part of the base game so people can get a bit more variety in their scenarios without having to worry about keeping "DLC requirements" low. It works like that in most games with editor and dlc content (for examle Arma 3 and DCS world) and it would also allow people to check out content before buying.
Well, then we just have to wait for the reconversion of the 266 class for TSW. https://store.steampowered.com/app/258671/Train_Simulator_BR_266_Loco_AddOn/
Might be possible to edit the class 66 in GWE. I mean, since all the content is baked, it would be hard to modify, but in TS19 you can add models to existing models. Not changing models, just adding new details to them, like that box thing and maybe, MAYBE PZB. It would take quite a bit of community effort to get it to work, though, if even possible...
Exporting 3d models should be possible unless DTG blocks it since the mesh is preserved in a cooked package. As for the code part you can make a new script that inherits from the Class 66 script and add extra features.