I like what Korindino has laid out.
The first step is (mentally & emotionally) disentangling what a "marriage" is/has been as accepted by society.
Half a legal contract.
Half an emotional connection.
Those two things can well stand alone and I'm one who feels they should anyway by default. But that requires reprogramming thousands of years of tradition. Seems it's going to need to happen on a one-by-one basis.
Once you get that separation accomplished each piece is much easier to work with.
Good luck !