I think the best thing is to expose JW tactics. The government could make sure that all these pedophile, blood transfusion, family shunning atrocities of JWs are published with facts in the news, television, and internet news very regularly. Sure, some JWs would be undaunted but many will be confused and ashamed. The regular public would be aware and would present these things to JWs regularly face to face.
Their children could be exposed to this info in school. Taking the JW children away from their family/siblings would bring on another set of emotional problems so I disagree to take their children away. As a JW kid, I would have hated the government to do that. (Fortunately, my 4 siblings and I all left the org in early adult years around the same time ((4 of us pioneered and went to Bethel too)) and we have a bond inseparable. We understand our exclusive sarcasm and humor.)
Also, the government could make sure, that no money by JWs could be sent out of country to the JW headquarters. The government could refuse the JWs any tax-free status. Also, the government could refuse any JW gatherings larger than a certain amount, say like no larger than 100 at any given time.