Get out of the marriage business all together.

The government is not the maker or the definer of marriage and should therefore get out of the business. There should be no marriages administered by any government official at any level. The license to marry can be administered by the government and licenses for the couples can be handled by the government as they are now. Marriage licenses for opposite sex couples, some other name for same sex couples. Let those with valid licenses to marry determine who can and cannot be joined so that the argument falls to a lower level where competence is increased. For example, the Catholic Church would be licensed to marry and would not have to issue any licenses to same sex couples while Joe down the street can also be licensed and perform the same sex ceremony of whatever name is decided.