It amazes me how much time and ink is spent on language and thought processes twisting some kind of grey area out of an abomination.
Exactly.
If you want a lovely chapel ceremony, a lavish reception and a honeymoon cruise, go ahead: that's what vendors (including -- ahem -- certain religious vendors) are all about.
If you want to co-sign on car loan or a bail bond, or a 30-year mortgage --- if you want somebody else to be your health care proxy, your financial proxy, or the sole heir of your estate --- more power to you: that's what contract law is all about.
None of this requires government approval -- a marriage license --- because there is no state interest (no civil, secular, public interest) in what you and your Extra Special Other have decided to do with yourselves for the nonce, for the weekend, or even for the rest of your lives. Two People In Love --- two adults pursuing their own fulfillment --- can do that on their own. Go ahead. No matrimonial certification required.
A public interest --- and hence, civil marriage --- arises only in the context of the one-and-only kind of sexual relation that can beget offspring: new human beings who are NOT adults, and whose identity, kinship and provenance are (usually, used to be "normatively") defined and sorted out by their origin in their parents' union.
That constitutes the core public interest in civil marriage.
As for all the rest?
It's a free country.
"We don't need a piece of paper from the City Hall."
Follow your bliss.
And leave me out of it.