Lock settings too with Power Off feature

The user joao esteves has already suggested something like this, that settings should be unavailable too if you use the power off feature, I will also suggest to prevent anyone to be able to make backups because I actually did this, from a locked FVD page, I just opened settings>made a backup of FVD dials>used other firefox>and loaded the backup and everything was accesible now. I know the power off feature isn't like encryption and Firefox (the browser I'm using) at least has the included feature to use a password to lock all firefox, but perhaps it should be 'code-worthy' to solve this "exploit".