I think the Consensus Cleanup should include a fix for the Murch-Zawy attack, in the form of requiring the timestamp of the last block in a retarget period to never be lower than the timestamp of the first block in this same period. In other words, the time span between the first and last block of a retarget period should never be negative.
We discussed it in this thread already back in August, but i figured i should mention it here as well.