Weather it is called a civil union or a marriage, should not the same legal contract be observed?
My preferred solution would be to classify all as civil unions and leave the term marriage up to the various religious intuitions.
There are historical reasons for marriage, yet there are cultures where a woman can have multiple husbands and cultures where a man can have multiple wives.
As a nation that separates church from state, we should have civil unions and abolish the word marriage from our legal texts.
Furthermore, like the French, priests, rabbis, etc. should not be able to make these contracts, rather only the agents of the state.
No religious cleric should be forced to perform these and likewise no religious cleric should have the force of law behind what they do.
The long tradition of separation of church and state should be maintained. If two people want to enter a community property agreement, so be it.