@ Timestorm: Good work!
I additionally removed the Startup-Sequence "S50wan" at /etc/rc5.d because I killed a SIM-Card - after a time it stopped working and had to be replaced.
I guess the reason could be that S50wan (resp. /etc/init.d/wan) starts and stops the modem - maybe the SIM was killed by often switching on and off.
Also this removed the modem-update sequence as the firmware of the modem is up to date and no need for further updates this time for me.
Additional removed S50updater at runlevel 3 (/etc/rc3.d) - because at this time I made a lot of modifications to the filesystem and updates would fail anyway.
Why?
Updates check the md5-hash and there is a very good reason for this: Not because of secrets or similar - no - the solution is that updates are made mostly by patching. An if you would patch modified files they could become unusable...
At least today I mounted a plug at the top of the kindle to easily access the serial-port for debugging purposes ;-)
Well as far as good - have fun!
Best regards Josh