Well If you didn't notice flood of I/O errors in rescueos then maybe it's not hardware.
In rescueos type command:
/sbin/modprobe g_file_storage file=/dev/mmcblk1 (or 0) stall=0 removable=1
and you will have whole emmc exported so you can use pc to repartition it according to for example
https://wiki.maemo.org/Repartitioning_the_flash
There is nothing special in emmc image (except same media files) so you don't have to flash it. Proper partitioning and then flashing fresh firmware it's enough. I was doing a similar procedure repeatedly in broken n900 except that I used sd card as a emmc.