Great job, NiLuJe!
"That may also make it possible to install official amazon updates on top of it just by deleting the trigger file of the hack (linkss/auto & linkfonts/auto)."
There is a way to do this automatically.
As you see, there is a way to allow stock firmware to be installed while a hack is installed. Kindle goes into runlevel3 for update, so, you can put a file in rc3.d to disable a hack temporarily.
Details in
https://www.mobileread.com/forums/showthread.php?t=87995
The link has a font hack also, similar but useful by utilizing runlevel3 to automatically disable font hack while updating a stock firmware.
I think you already read that, since you left a post.
Automatic runlevel3 switch in your hack would be really nice.