Good plan. Let the state offer marriage ‘contracts’, and the churches offer services of ‘Holy Matrimony’, to whomever meets their religious requirements.
Since marriage is now a right conferred by the law of the land, license, contracts or whatever you want to call them should be under the purview of the federal government, not the state government. The state should have absolutely nothing to do with the issuance of licenses and/or contracts. Let it be handled by the HHS, the Social Sec. Administration, or the the federal court system.
Churches that want to conduct religious ceremonies are free to do so for whomever they wish - and those who do not are free to do as their religious convictions lead them.