The New York Times had an interesting article recently about marriage. Among other things, it outlines the history of which institutions could declare a marriage to be "valid" (e.g. the Church or State). For a long time apparently nobody cared -- if you said "we're married" that was good enough. Times changed and people started to be need to have proof of marriage -- for example for inheritance, so institutions filled the need.
So why not create a "National Marriage Associations" that is an independent, non-profit? It's sole purpose would be to certify that other independent marriage association bodies meet some agreed on set of minimum standards. Then governments and businesses could just require a marriage contract certified by an accredited association. (Just as they might require a degree from an accredited institution of higher education).
If I wanted a full-on, all-the-trappings religious marriage contract, I could get a church to issue one for me -- assuming it meets the basic Marriage Associations minimums. The church could add on any other clauses it wants, like no sex on Tuesdays or whatever. Government and businesses that want to see proof of a spouse's relationship would still be happy. On the other hand if I wanted a Las Vegas Elvis wedding, with pagans and machines guns, that would be fine too -- again, as long as the basic minimum standards are met, who cares?
Time to write your representatives.
I worked with a guy at Yahoo! named Jeff Bonforte who claimed he was going to write a book called Marriage 2.0 which would outline all of the legal documents you need to get all the benefits of marriage (medical decisions, inheritance, etc.) without all of the costs, specifically AMT and other taxes punishing the married wealthy.
I tried to convince my wife to do this, but she wouldn't buy it. She also still insisted on a traditional wedding and a diamond ring.