I think you'll need to replace the mainboard with one from ifixit. Not aware of a debug interface, but in the absence of that, you'll need to desolder the nand

I think you'll need to replace the mainboard with one from ifixit. Not aware of a debug interface, but in the absence of that, you'll need to desolder the nand module and replace the files there with the help of another owner. The mobile read forums are where you can connect with fellow owners. So the short version: I'd replace the mainboard.