@Flohack Regarding the user-data folder, it took at least 30-35 minutes to backup 12Go (including compression) over usb2.0, and nearly the same (a little faster) to restore (arround 20 minutes).
The system-data folder was smaller then it take less than 5 minutes to backup (and 3 more to restore).
I was thinking about doing it on the SD at the beginning but as my data partition was about 54Go, I was scared that my 32Go SD card wasn't sufficient (as I already had a lot of things on my SD like all the pictures taken by the camera, they are very big on te Pro5 because of the sensor quality).
And one other thing was that my sdcard wasn't mounted on recovery, I think that the recovery-turbo.img miss a lot of features.
For the phone where the system-data and user-data are correctly mounted on the /data folder in recovery, this script can work well if you remove the line "adb shell mount /dev/block/sda44 /data"
But if you want to do that locally on the SD card, if it is mounted, you can do that on the recovery nearly the same way, don't forget to use tar as it will take care of the symlinks (not to ignore them, it will save them too).
It will be very perfect if that can be integrated to the installer !