Eric,
I just reread what you said.
I don't think there's any harm in prompting the user for a password when he hides the account settings. If the user decides to use the same pw as the MPW, that's up to him...
If I understand this correctly, you want to prompt the user for a password, when the box to hide the settings is selected and the password, which is typed here is independent of the MPW. If that is so and I believe it is, you have just come up with another splendid solution.
I am looking forward to the implementation of this feature.
Sincerely,
Romeo