The problem that was to solve was that freestyle doesn’t support panoramic cams – especially equirectangular. The solution was to create 6 renders (cube projection) with freestyle applied and create an equirectangular render in a second step from that with the prerendered cubes.
It seems that we have accomplished a sufficient quality. Next step is to add a sterescopic sphere like we did with the low quality render before.
Here is a link to the photosphere as well as to the original combined image.
and the image itself: