Officially recognised "Civil Partnership", with full legal equivalence to "Marriage", seems to work well enough in the UK, among other places.

What's wrong with that as a way of avoiding hassles about what is really a matter of dictionary definitions?

And of course, since people use language how they wish, people getting hitched in this way often do refer to this as "getting married" and send out "wedding invitations" etc. So in time, regardless of what the law says, maybe the dictionary definitions will change - and there's nothing any court of law can do about that.