I think the enforcement of payments should not be an exact date but rather we say for example it will be turned on within a month so every pool that has not updated or is currently cheating on masternode payments would get punished... So there would be incentive to update asap to the latest and stop cheating on payments..
I also think enforcement should be ninja launched we cant advise adversaries as they may put more hash into RC4 pools.
Edit: For now lets just keep promoting voluntary compliance as that is the best way to go and we have achieved very good results in the past. After they update, pools that are not paying 20% should be advised that their blocks will be rejected if they dont activate the 20%, but that should be a second step.