possibly. the problem, though, is that 85% of signal's users would A. hate it and B. not know how to shut it off (even if you told them). that's part of the problem with trying to deliver security to the masses (and similar to the backup problem that they used to have).

fwiw, as far as I can remember, the signal foundation's position has always been "once someone has physical access to your device, all bets are off."