Sorry, in case it wasn't clear I was answering the question in your last paragraph:

wouldn't it be possible that every account holder had the option in his own account to either select a 4 or 13 week power down?

by pointing out that, yes, it is certainly possible, but not possible within the constraints set forth for the current hard fork. It would have to go into a future one, probably in six months to a year. For this one, the options under consideration are simply 4 weeks or 13 weeks.

Your other ideas (2FA, whitelists, etc.) are also very good ones which should be considered in the future.