Decoupling those concepts removes the whole debate.
The reasons for the state incentivizing men and women getting married are gone or at least no longer prerequisites. So since we like the financial benefits, even though the reasons are gone, just expand the state-sponsored concept to any combination of humans that want them. Any opposition is clearly religious people viewing their government as an extension of their religion, or just completely conflating the concepts that coincidentally have the same name, and they out themselves making it easy to ignore.