Powering up was not made for these purposes and there's no reason to believe it will behave well for these purposes just because it apparently has for you so far.
As far as I know, Powering Up was intentionally made long in order to ensure that the people who vote for witnesses and participate on the social aspects of the Steem blockchain have "skin in the game" and I think that definitely applies to exchanges.
Exchanges barely have any skin in the game since their Steem will be other people's money.
This is like using a ziptie to lock your front door when keyed locks are readily available. Sure, nobody's come along and cut it yet.
Sometimes it's possible to use things in ways that they were not intended for, and MANY people are using Steem Power as a form of security.
If you increase the holding time possible on the Savings feature BEFORE you decrease the Power Down time, it would erase the need to use Steem Power as as security feature.
But @thecryptodrive is not planning on doing that and I don't think you are either and your comparison of locking your door with a ziptie is not really valid.
A better comparison would be logging your door with a lock that's just as good as a door lock but not intended for doors but was improvised instead since there were no door locks in the town that you resided in (makes sense).
Think about it...