Realistically, there should be a separation between marriage by churches, and what they support in their ideologies, and states sanctioning unions for the sake of benefits and support systems.
One really has nothing to do with the other. People who want to get married in ways their church doesn't want are people whose values are at odds with the church. So they need a different church. Their version of sanctioning a union before their god has to be oriented towards their beliefs, or their faith means nothing. I am all for the churches collapsing as a result, but that is another matter.
State/ government sanctioned unions on the other hand are merely a paperwork play that connects people, gives them rights with respect to assets, income, etc. They can still do it with as much or as little pomp and circumstance as they desire, but that is all that it really is from a government perspective.
Abolishing institutional marriage would make sense and ensure equality. It would solve arguments over marriage laws. The perks of it, such as leaving property to people, and hospital visitation could be done through contracts. This could also prove more effective and less argued over than putting them into the marriage system.
It is forcing your religious views upon the people of this country. Marriage should exist as a Ceremony for religious people to participate in but should hold no legal ground. There are other religious bonding ceremonies other than marriages so legal marriage is unconstitutional and discriminatory. Legality of people living together should be handled by the government not a religion or religious beliefs. People in government should not let religious effect their politics. The use of of marriage and religion in the government goes against separation of church and sate. Like using the bible to say why a law should or should not pass is not right the bible legal should have no standing as a valid argument, or evidence. Believe what you will, but please keep your religion out of my government.