Hi Aurelienri,
What I meant was remove all your "Partition" actions from your template. Create an action that injects the diskpart script that I posted above. Create an action that runs diskpart with the script. run image X apply. Run BCDBOOT
Instead of the partition actions it would look like this:
1) Inject diskpart to x:\temp\diskpart.txt
2) run diskpart with /s X:\temp\diskpart.txt
3) imagex /apply to your C (or w) drive
4 run bcdboot to create the system boot files in the system partition