... burn 5% as a fee to do so ...

That's a really interesting idea but doesn't change the fact that in case your account got hacked, with a shorter power down period the attacker could get a bigger portion of your STEEM before you would have the chance to change your keys.

Maybe 2 FA should be implemented in the long run.

Maybe there could be the option to determine save withdrawal addresses (white listed addresses)?

Also, 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?