@olive-tree The issue with WDS/MDT is that the image is purpose built for the target hardware. So the WIM file may not contain the entire image as MDT will add software or drivers based on the target hardware. MDT uses file level cloning where FOG uses block level cloning. Those are two different technologies.
Now you might be able to take a fully deployed MDT image and then sysprep it and recapture it with FOG. In a way that is what I do on my campus. I use MDT to create my golden image and then I sysprep that MDT created image and deploy with FOG. That takes me from about 1.5 hours to build an image with MDT to about a 20 minutes (bare metal to user ready) to deploy with FOG.