I don't think stitching portions together would be fast enough, so timing would be an issue, especially since you have to move the camera, and then take the snapshot. It needs to happen at start of layout, plus you wouldn't want anything else like an animation to get into the picture.
Not sure what you mean about plot a dot. I need to preserve the texture.
Yeah, I don't think "portal" rendering would work well either. Generating hundreds of tiles when ever the view point changed would bog down the system.