I love free-markets, and strongly believe that monopolies are evil. So why should marriage be the exception? I think we should privatize marriage. This means ending the state-monopoly on marriage, and getting the government out of our lives for good. Instead, couples would draft their own marriage contract that, within some limitations, would be enforced by the courts like any other business contract or partnership.
The result would be that the gay marriage debate would become irrelevant, and more fluid arrangements suiting the respective parties would be possible. For example, more than two people could enter the contract. Moreover, it would end unfair treatment that married couples receive, and would better cater to individual preferences. Home makers, for example, could easily demand an alimony as compensation for putting their careers on a back burner.
Finally, such a system would benefit women and the gene pool. With more possibilities, multiple women could marry a wealthy man and enjoy legal protections suiting their individual preferences. This would mean that, since wealthier men tend to be more intelligent, the market would improve the gene pool since women would have incentive to marry them.