Also: This means that basically all of their safes are compromised by design. You can neither be sure that your posessions are safe from being stolen nor can you be sure that nobody is able to plant incriminating things into it. And you wouldn't even notice it.

There's absolutely no reason to have a master-key for your safes from a buisness-POV, actually it's detrimental to your buisness. If someone was dumb enough to lose their keys, you have them find their own way to access their posessions and sell them a new safe afterwards.