How to Solve the Same Sex Marriage Problem

I'm not sure why the following hasn't been seriously considered or discussed, but there seems to me to be a clear solution to this whole same sex marriage issue. Make marriage a religious ceremony/bond between people who the particular church allows to be married, which in the vast majority of churches is a man and a woman. Call it marriage, finis. All non-religious ceremonies are, by definition, civil unions, whether between a man and a woman, woman and woman, or man and man. Both marriage and civil unions by law need to have the same rights, privileges, and responsibilities.

Let's look at this from a couple of perspectives. If I'm a proponent of gay marriage, I get a union with exactly the same rights as a couple who is married today. If a church recognizes that gays can be joined in their church, then they can be married in that church as a marriage. If I'm someone who believes that marriage is strictly between a man and a woman, gays or lesbians would not be married in my church but joined by a civil official in a civil union. What if a man and a woman are joined outside the church? Most likely they are not very religious so it makes sense that they have equal status but not so in the eyes of the church. Church and state are separate but equal (one of the few instances were it works).

My proposal doesn't force any church or religion to modify their beliefs or practices. It allows same sex couples to form equivalent unions outside a religion. Other than hate or seeking to control others, why wouldn't this work?