Considering tribes and race are less of an issue in Hydaelin than in Vana'diel, the core of marriage IMO should be determined by city state.
Like say Gridanians have the chapel/sanctuary of the twelve, but traditionalists prefer to have the ceremony held in the forest itself (probably somewhere around Bentbranch), presided over by a conjurer and traditional gifts are foodstuffs since the celebration banquet held afterwards is a communal effort of those invited to honor the newly married couple.
In contrast, Ul'dahn weddings are presided over by a thaumaturge (or two, one following Nald and one following Thal) and are generally themed around "paving the road" and wishing good fortune to the happy couple (if I recall, the post I wrote for this on the beta forums had the couple get a small gift in money and get showered in flower petals - flowers being incredibly valuable in Thanalan given its arid conditions).
Lominsan weddings would be presided over by a representative of Maelvaan's Gate. Instead of being entirely faith-oriented like Ul'dahn and Gridanian ceremonies, arcanists act as a representative of the government to oversee the ceremony and make it official (kind of like the mayor of a town presiding over a wedding or a representative of the state/region's governor). Llymlaen is still evoked in a way, as the ceremony would make the point that just like the Navigator guides the denizens of the sea, so must the couple lead each other into a brighter future, together.
This is stuff off the top of my head and trying to recall the post I made about it on the beta forums. Wish I could remember more. =/