Except for the fact that it would cause chaos in Britain, it seems to me that the best thing for the EU in the long term would be a no deal BREXIT. That would be the "the common people know what they want, and deserve to get it good and hard" (H. L. Mencken) approach.

The resulting British economic and social disaster, and subsequent on-her-knees begging to be let back in even without the Thatcherite rebate exception would probably scare away any discussion of EU separatism for quite a while.

Too bad about the English people, but hey, the Article 50 vote was their clear and final decision, right?