Hi André,
thanks for giving me some starting point. To be able to recover the files, we had to attach the disk to a windows system. There we used Diskinternals (VMFS recovery edition). In attachment all the log files + non-flat disk files. Also a list of all files of this VM.
As explained, the files do look a bit weird. Also there is always an exact copy of a file but then with the extension _OFSBC1. Not sure if there's a difference.
I was very happy when I was able to recover the files, now I'm getting stressed again because they look weird and might not be recoverable after all. I'm also in contact with Disk Internals. Because when I started to try and recover, it didn't work. With their help I was able to recover. Now I'm also asking them if the format of the files can change to this result and maybe there is a setting we need to change on recovery process before we can start merging flat/delta files...
If the vmdk files are only partial recoverable, that is also an option. As long as I can get 2 specific folders out of it 
...
Thanks for all the help!
