Amusingly (or not), the UK went to all the effort of introducing "civil partnerships" which involved exactly all that upheaval, about a decade before just intro

Amusingly (or not), the UK went to all the effort of introducing "civil partnerships" which involved exactly all that upheaval, about a decade before just introducing equal marriage, which then led to a load more effort to allow porting a partnership into a marriage, as well as leaving partnerships in place for those who do want one or already have one.