I am unsure if you want to just place the downloaded image file onto that partition or if you want to extract the image file folder by folder as if it is an installed system? Is this a workable way for easy debian at all? As i said, do not know much about it.

The difference: The script would look for /ed/debian*.img* , if you configure it in /home/user/.chroot
while the latter will have folders /bin, /etc, ... in /ed