If marriage is defined as part of a religion, then enacting a law that expands or restricts it would be a first amendment violation. What I am suggesting is if they define all relationships as a domestic partnership, gay or strait, and let the label of married be up to the churches their would be no discrimination.
I do believe that Gays should have the same rights, and they should not be "separate but equal" like what was done to the blacks.
So if Joe and Jane are together, and they get married in a church, and receive their license from the state. Then according to the state they are not married but in a domestic partnership. Which has all the benefits of marriage today in law. Then simply allow the gays to do the same thing with the state.
Only in the eyes of the church they are part of would Joe and Jane be married.
The difference is the church has the right to choose who is a member and who isn't, and they get to choose who they marry as it is defined as a religious ritual or symbol.
Therefore in the eyes of the law, there would be no distinction, it's all domestic partnerships. However in the eyes of the church there would be a distinction. And your status as husband and wife would only be official in your church. (though people could still call you that).