I'm just messing around with the shader tutorials an I tried to wrap a texture around a model which works but uses the UV Set defined in the model.
Is it possible to wrap it around the model regardless of the given UV Set of the model ?
The Point is that I deform the models at runtime but the textures should keep their proportions no matter what size the model gets.

differs on what you do. You can use a material matrix for fixed functions iirc or you can just read different coordinates from the texture in a shader
like
color = tex2D(texture0, texcoords.xy * 2); // with 2 being the scale factor

you should try triplanar projection. use world coordinates and blend the textured based on the angle to your x, y and z axis. it's not trivial but works very well.

Thanks for your replys, the next two weeks are packed with exams so I'll give it a try as soon as I got more time.