I also tried replacing charge_only_mode with a sh script that rebooted the phone but only got a red circle with the M (on a Motorola Bionic). Changing the script to the below got it working...Now I get the red circle with the M for a few seconds, then a blank screen, the another red circle with the M, and it boots on up.
#!/system/bin/sh
su -c "/system/bin/reboot -n outofcharge"
