PROBLEM
Its a common practice among engineers to copy their client's keys without them knowing when they install locks. This is only really problematic from an RP standpoint because it can be done in full view of other players who have no mechanical way to perceive it.
WHY ITS A PROBLEM
I'd argue that the chief mechanic to avoiding having your things stolen shouldn't lend itself so easily to having your things stolen-- especially in a way that totally subverts the lockpicking skill and the whitelist/investment that comes with it.
SOLUTION
While I think its important that there be space for shady businessmen, since players can't be trusted to behave in good faith I suggest that a forced emote be implemented when players use a blank key (in the same way that rope forces an emote).
ALTERNATIVE IMPLEMENTATION
If we wanted to retain this feature in some form, the ability to copy keys secretly (emote-free) could later be a hybrid perk (lockpicking/engineering?).