I just finished my code to boot kindle touch or k4nt into diags or fastboot mode in USB Downloader (also known as USB HID or USB Recovery) mode. I will post it in the k4nt and touch wikis, then post an announcement in a new thread (and here).
In diags mode you can export the USB Drive to make changes to it (add RUNME.sh repair script).
On the k4nt you can open SSH in diags, or on the touch you can push a reverse shell in diags. From a shell you can examine and repair what prevents main from booting. You can also restore mmcblk0p1.img on the USB drive to /dev/mmcblk0p1 with a "dd command.
Or, in fastboot mode you can reflash the main partition from mmcblk0p1.img on your host PC using yifanlu's kindle fastboot tool.
Beware that these methods are risky if you are not careful. Do not flash the wrong partition. Do not delete the wrong scripts.
I will provide instructions and tools.
Last edited by geekmaster; 02-18-2012 at 02:29 PM.