I don’t think it’s that complicated actually. The solution is to remove privileges from organisations that promote shunning as policy, not to punish individuals who follow shunning practices of such organisations. So we would allow organisations to practice shunning but remove charitable status or tax exemption and other privileges from these organisations. This would be accompanied by public information explaining the reasons for this approach and the harm caused by shunning communities. This solution avoids any problems surrounding personal freedom because they can still shun if they wish, but there is a reasonable public stigma involved in promoting this practice. If this approach was adopted I think we would be amazed how quickly Watchtower and other groups would drop shunning practices. Or if they didn’t they would suffer significant, and justified damage to their reputation.
It's not about somehow forcing people to talk to other people. Human relations are complicated and cannot be regulated in this way. It is about getting the organisation to remove shunning practices from their literature and policy statements, or allowing them to suffer reasonable reputational and societal consequences if they refuse.