Marriage is defined as many things, among them a sacrement. The government should have nothing to do with sacrements. Thus my preference for the term "civil union" regardless of who's marrying whom. In many European countries, couples have their relationship recognized by their government through a civil union and then have that union blessed by the church of their choice in a marriage sacrement. And yes, it is within the power of that church to deny someone the sacrement of marriage.
That makes sense and would seem the smarter way to go with it. Then none of these gay marriage laws would be an issue. I'm sure some people would still take exception to churches denying their sacrament ("marriage") but at least then it would be the churches problem and not yet another trivial thing for the government to waste time and money on. And really shouldn't even be an issue there either since I would think any self respecting person with half a brain wouldn't care about a sacrament approved by a group of people who are foolish enough to think they have the right to tell people what is and isn't "moral"(acceptable).