The current power-down period has its advantages. However, we cannot skip the fact that some people would not like to lock their funds for so long. As beneficial as it is, some might not power up because of the power-down longevity. If we can power up instantly, there should be a considerable powering down time to strike balance. In the case of losing keys, if any fund would be stolen as a result of that, it would take 7 days for the perpetrator to have his/her way except if it's a hack (Talking from the perspective of powering down). And to be candid, we've not had issues with that. If we've encountered that at some point, it's below 2%, so I would say that point isn't enough to say no to a considerable power down period.
I read some comments before dropping my opinion, so don't be confused.