The final video is not going to consist of the raw images. It will be compressed video and will not be able to tolerate as much dynamic range as the raw images are able to tolerate.
I don't think that's correct. The RAW files are 12 bit but when you export to JPEG they get remapped to 8 bit and don't suffer the same issue. The same should happen for the video file. You're right that it doesn't have as much dynamic range but it shouldn't matter as the values get re-mapped. You can see the effect in the image attached below . . . not the purple areas in the bottom corners. When exported to an 8 bit JPEG the image is fine as the data is rebuilt from the original RAW file. But when exported as a video it looks like the video is building from the preview images (hence why I get the purple patches) and not the RAW file.
The raw file has to be converted for the slideshow. The slideshow, what ever is going to play it, it is not going to be able to display raw files. I don't know what is happening, and why you are getting the purple artifacts, but you cannot expect raw images in your slideshow. They can be used by Lightroom to create the slideshow and they probably are. But they have to be converted to pixels.