I agree with @aggroed. Also +5% burn for instant power down. But considering potential compromise from instant burn to powerdown as highlighted by @smooth, can we setup up a max cap for instant power down ? For instance maximum of 10%(TBD) of your SP can be instantly powered down with 5% burn with cool down time of 30 days for the next use thus if you want to use another instant powerdown you need to pass 30days from the last instant powerdown date.

Time to time people will need some urgency of liquid funds in their life regardless of how much they love about steem. Life is no guarantee. ;)