Digging more in the different VTK classes, trying to understand the logic of how “items” are displayed in a 3D view and texture is applied, I am getting the impression that I should possibly try the opposite way than starting with a “filter” and try to “hack in” also the functionality to apply also the actual texture - which is basically the job of the “representation”.
I might instead have to derive an own “representation” plugin that extends the texturing feature to reading and evaluating georeferencing info, generate the texture coordinates from it and do the actual texturing. Maybe this would also open the way to stopping the automatic tiling - which is not very useful in the case of projecting maps or aerial photos on a topo surface!