my only issue with 2 user authentication is when the "crap" goes sideways at 2am
it could be a new sql agent job or a new process from an app, but you can't fix it until you wake someone else up.
it reminds me of those scenes in movies where you have to have 2 people put keys in and turn at the same time to arm or disarm a device.
I prefer to trust my DBA, but you might think about using a temporary passkey (say 2 hours) that triggers an audit trail
Like I said, I prefer to trust people like steve (and Dino) rather than over engineer change control