Hello there!
I wonder if it would be feasible to implement a keypad scrambler on/off button/key for the lock screen?
E.g. by initially placing it in the bottom row, next to the zero and make every key (including the scrambler on/off button) shift position randomly every time a key is pressed. This will also allow the scrambler key to act as a “make no input”-key in order to mask the actual number of digits/characters in key.
Will it sail?
There is Scrambled lockpad (SFOS 3)-patch (patchmanager3 web catalog). But it scrambles number positions when the lockpad opens only. Not after each key press. But that could be a starting point.
Or did I understand correctly?
I liked the old patch so much I forced it into an incompatible SFOS version once.
Not a good idea but a clean install sometimes clears the atmosphere. 
Yes, that is some of the functionality. But in order to go full tin foil hat, it will need that extra scrambling, though. And I have no idea if it would be possible to implement this without a blessing from the SFOS core developers, i.e. getting it integrated in the OS as such?