I'm pretty sure "change them all to civil unions" is intended to mean "shall be considered as marriage by whatever name, minus religious issues". If the law can't actually support that concept then I suspect things get "interesting": I fully expect all of those cases you mentioned and more will be thrown up by the anti-SSM folks as examples of "rights" that will be "lost" if SSM is enacted. Or, quite possibly, be used as a large set of legal issues to be tried in court in order to delay the implementation of SSM.