After loosing all data on a completely discharged Nexus 7 (look here), i decided to encrypt the storage with my own password, so that i should be able to give the right pin into the "type password to decrypt storage"-question (hopefully).
never loose my data again
on every bootup i have to enter my new pin....
select "Encrypt tablet". If your tablet is not plugged in and not completely charged you get:
After plugging in and charging you get:
Tapping on "Encrypt tablet" leads to:
Ok... Irreversible and many reboots... Scared? ;-)
And after some reboots i had to give my password to decrypt storage for bootup:
(This is exactly the same screen, which was shown after rebooting the completely discharged Nexus 7. So hopefully after next complete discharge, i can start the Nexus without loosing all data)