JasperW,
As I’ve already mentioned on Reddit thread & on my blog, going from Windows VC 6.0 to VCSA 6.x would not be a supported route with the Fling. You must go from VC 5.5 to VCSA 5.5, once you’ve have successfully migrated to VCSA, you can then use the traditional method of upgrading to either VCSA 6.0 or 6.0u1. There are major differences between vSphere 5.x and 6.x and hence why you’re seeing it’s looking for things that don’t exists and the Fling was built prior to 6.x being released.
You might also be interested in this Tech Preview that we showed off at VMworld which would cover additional source configurations. You can find more details here http://www.virtuallyghetto.com/2015/09/tech-preview-of-windows-vc-to-vcsa-migration-at-vmworld.html