[Seb-C]

> the systems and conventions need to change?

I think that in many (most?) countries nowadays, marriage is already no more than just a legal status that offers those practical points, so I am not sure if anything needs to change.

You don't have to get a ceremony/ring/party, go at the church or whatever your culture/religion associates with the act of getting married.

You can just sign the contract privately, which makes you legally married.

Same for divorce, I believe it only gets complicated when you fight about children, money and assets, otherwise you can both just decide to stop the contract.