It seems that when you talk about difficulty adjustements in terms of time, it really means "In X number of blocks at the expected block generation rate".
So you would have to come up with a new method of recognizing difficulty reduction and performing it "on the fly" (between blocks) in every client at once in order to have the difficulty drop at your desired emergency interval.
It probably wouldn't be too hard to program in. at so many minutes after the previous block's time difficulty is adjusted by a predetermined amount?
At one point I thought there was a recovery method like this built into bitcoin, but then i found out i was wrong.