All those are commercial concerns, and will run afoul of discrimination laws, because they are supposed to serve ALL of the public. If 'legal' marriage is removed from the purview of religion, then what happens in religious ceremonies is NOT a public action. If churches only confer a religious covenant ceremony on members of their faith traditions, then it is something that is covered under the 1st Amendment Freedom of Religion, and could be argued, Constitutionally, on that point.
So if part of the teaching of the Catholic faith is that ONLY one man and one woman can marry, then that is the only kind of ceremony that can be allowed in a Catholic Church. So a couple could receive the Sacrament of Matrimony without being 'legally' married. This might be a good thing for older folks who would like to be married, but could have a problem with how pensions or survivors' benefits are handled if one is re-married.
The end around is through tax breaks that hang over Churches’ heads. A Church that fails to adhere to State sanctioned homosexual “marriage” will eventually be compelled to conform through some type of coercion; that will be the next step. Heck, the dust is still not settled with abortion/artificial contraception coverage where the First Amendment could be usurped. In some States adoption laws have stifled the Church already. Satan never sleeps, especially with a living Constitution and corrupt Judges everywhere.
You seem to imagine our government cares what the Constitution says.