really, adding a marriage system into the game is a very minor addition to the game. In Final Fantasy XI (the previous Final Fantasy MMO) all it really amounted to was a form you had to fill out in the POL Viewer, a fee you had to pay in gil, and then once that was taken care of, you would receive a ring each for the Bride and Groom, and a service at your choice of location officiated by an NPC. As an optional additional service for an additional fee, you could also purchase a wedding gown for the bride.

There was nothing intrinsically game breaking about these features. The problems that arose with the Wedding Service were entirely the fault of the players and not Square-Enix. It was the fault of Players who decided to share their items between the Bride and Groom who ended up getting ripped off by their spouse when the relationship went sour. This was not the fault of Square-Enix and as such Square-Enix was not liable for it as they did not make a shared Inventory Space part of the Wedding System in that game.

I see no reason why Weddings would pose any problem in Final Fantasy XIV: A Realm Reborn.