In case anybody is interested I have some more stock of my C128 video mux boards that convert the output of 80 columns into analogue RGB AND s-video. There are both PAL and NTSC versions in the shop (it's about colour encoding only as vsync is set by the VDC)
It's REALLY hard to get a good photo of the output, but honestly, you can't get better from the 128. The S-Video out from the VDC is as good as it's possible to get with S-Video. All the colours are correct with the brown fix too.