Yeah, instant power downs would be a serious security risk. That's always been one of the selling points of Steem, that you can recover your account with funds intact if it gets hacked due to the long 13 week power down period. I've seen it in action with @surfermarly, her master key was phished, but she was able to recover her account in time with no monetary losses. So this needs to stay.

But you could add to it, like an option to enable an instant power down if you're willing to take the risk. That would have to take some time as well though, like a month. That's plenty of time for someone to return from a vacation and stop any hacker activity. 2fa wouldn't hurt either in enabling this feature.