I mean I like the idea but we don't really support account sharing, so I see this as going against our rules because it's a suggestion based off of something we don't personally agree with. With that being said, I do think that people should be more careful when it comes to sharing their account, after all it is their choice but it has its downfalls and I can say that a few people are banned right now for account sharing (they share their account and the person hacks). Regardless of this though, it is "extra-secure" but I would only see this useful when changing the email. Oh and I would rather it be generated by Dave because players can use PINs they're familiar with such as their birthdate or a special occasion or a school-related PIN number, things that others can guess too easily.
