They've said it won't be a hassle. You do the quest, you can have a ceremony if you want, not sure why people think the Sanctum isn't instanced, because it clearly will be since it doesn't actually exist in game yet(all you can do is see the outside of the building and walk around in the entrance garden), so there's no "booking a venue".

From what's been said a whole bunch of things are optional, even the costumes. You don't have to buy the special two seater mount, but considering the other one is a heck of a lot harder to obtain, I don't see why you'd pass up the chance, same with the costumes.

The system is symbolic though, you're not actually getting married, you don't suddenly have rights to a person's belongings or account. Don't be silly. It's meant to be hassle free.

I expect the website application thing is just a "bad idea" being tossed around and ultimately discarded, given that it will 100% guaranteed break on Day One for a week or so if they do it that way.