I keep wanting to turn that inside out and say—deal with every requirement this way, make this the default, make the threshold of cost/schedule/risk impact for triggering change control be 0.0 in all cases, have the Change Control Board meet every week, have them assess the impact of every item and decide whether or not to schedule it, have no other way to schedule any activity than via the change log. And bingo! Your project would pretty much be agile.
In fact, I might just do that.