If the institution of marriage really can't survive without government sponsorship, then it's high time for it to be "deconstructed".
There are things which Western (and other) nations have traditionally done to preserve civilization, society, peace, institutions. Conservativism, in my opinion, is not about destroying all vestiges of these traditions. The fact that socialism and cultural deconstruction have made government incredibly intrusive is lamentable. However, the solution, in my opinion, is in traditional Constitutionalism. That would mean reversing or modulating these bad effects - not adopting radical libertarianism.
All that said, marriage is one of those traditional institutions which it is appropriate for government to be involved in, for reasons that have been enunciated on these threads over and over. The awesome power of the state is appropriately used against those who would dishonor their familial obligations, because that behavior leads to societal dysfunction - probably causing greater dependence on nanny statism.