Reducing the powerdown period to 4 weeks is not a good idea imo, and will not attract new people as 4 weeks powerdown is still a time delay that still deters people from powering up. All it does is allow hackers to have access to larger portion of the funds in 7 days.

I would say keep the powerdown period at 13 weeks and allow users to opt-in an ability to do an instant powerdown with a 5% burn with their owner key, which will only take effect after the 30-day account recovery window. They will be warned by the interface that "by proceeding with this operation, your funds stored in vesting will no longer be secured with the time delay". Of course, users can do the reverse and disable the instant powerdown, which takes effect immediately (no 30-day waiting period) and can safely be done with an active key.

The instant powerdown feature may be initially set to be enabled/disabled at account creation.