There should be no need to edit meshes, assuming the trunnions are correctly placed... (I guess I could make a diagram with that...)
The orientation of the payload is dependent of the parameters of the attachment. The position of the mesh is dependent on the position of the attachment, which should be a trunnion, and the picked PLID to locate it in the PLB.
The basics should be working, but that feature needs D3D9. I still need to work text into the image to show pan and tilt angles, managing video sources (a set of hacks in real life) and turning the displays off.