Thank you to you both, meltdown and Thor, especially for sharing the script and pointing to j0534ng31's instructions (https://www.mobileread.com/forums/sho...1&postcount=28
For the record: in order to accomplish step 2 therein - installing the driver - on Win7 64bit I did the following:
- Taking linux-cdc-acm.inf from http://www.kernel.org/doc/Documentation/usb/
- Copying the contents of the mdmcpq.inf folder (starting with mdmcpq.inf_amd64_neutral in C:\Windows\System32\DriverStore\FileRepository\ on my machine) into the same folder where I put the inf.
- Modifying the DeviceList in the inf - here it took me some time to realize that the serial/USB-bridge in recovery mode has a different VID and PID than the T1 when connected normally (rather logical, but I just did not get it in the beginning...). I used USB\VID_0525&PID_A4A7.
- Pointing the driver install dialog to the folder with the inf as well as usbser.sys and friends, giving me a connection to the T1 on COM8.
Then it was easy to fiddle about with PuTTY as suggested by Thor. While I also used your script, I additionally just dumped the whole "disk" /dev/mmcblk2 to the external sd - should make a quick entire restore easier, which, however, I did not try yet.