Hello stereoV!
Thanks for the post. We already know about the Texture Manager, but unfortunately, there's not much we can do, because it's a C4D feature. We will see if we can come up with some clever way of supporting the Texture Manager, but it will probably be quite laborous.
As for the Shared Shader problems - we also know about a few issues, but just to be sure - could you describe the setup that is not working for you so that we have a reference? If possible, it would be ideal for us in you sent a scene where the problem occurs, so that we could use it for debugging.