I’m happy to see the interest in modding for Train Fever. As we’ve told before, we’re working on the modding features after the release.
We’re using a converter to get an .obj + .mtl model into our game. A train is separated into different meshes which can be instanced several times.
So basically you can create your trains already and include them when the tools are ready. You’re going to need one .obj file for each lod (level of detail). You could change the materials in every lod but it’s not necessary.
The animations are mostly done in our scripts. Wheels and bogies are working automatically, they just need to be separate meshes.