I disagree with your advice. You are advocating duplicity and lying (if it is arranged to have a young couple not be ready, it becomes a real issue, morally and legally).
My advice is much simpler - announce today that the church will no longer be performing weddings. Weddings are not a New Testament mission of the church. Far better to stop the periphery benefits offered by the church than to be sucked into a dishonest charade, or violate the moral foundations of Christianity.
this is they way to go
However parishioners who meet the church screening standards for adherence to church doctrine can be offered special religious services to bless their marriages that have been registered by the government
similar to Europe where people have civil service to get married legally and optional church services to bless their marriages
Ministers and priests will no longer be licensed by the government to perform marriages. No great loss. Go to a wedding registry in city hall. Church marriage returns to being a sacrament. Church membership in good standing and public statement of faith returns to being a requisite
Thank you for your comment. The issue of duplicity jumped out at me too.